Why did the Great U.S. Collapse of 2019 occur so rapidly, and what set it in motion? Looking back in a recent article, the Swedish scholar Inga Stenmark acknowledged various long-term causes but stressed a chain of short-term events. According to her research, the first domino fell on November 9, 2016, the day after Donald Trump's surprising presidential election victory. "This was no Kristallnacht," Stenmark noted, referring to the violent pogroms that had occurred in Germany on that same date in 1938. Instead, her research had taken her back to a tiny incident, "seemingly no more significant than the flutter of a butterfly's wing." It occurred, she explained, in Iowa City, Iowa, when a boy bumped into a fellow student in the cafeteria at West High School.

Hardly headline news. But the person being pushed, a fifteen-year-old American girl named Lujayn Hamad, was wearing a hijab. Her pusher allegedly swore at her and told her to "Go back home." Ms. Hamad's story should have ended in the principal's office, but instead, on November 20, it appeared on the front page of the Sunday New York Times. According to the researcher, the tale from the Heartland touched jittery nerves. Stenmark's investigation showed that Times readers reacted with predictable dismay. But at the same time, she found, cyber-trolls seized the topic and set up a poll on a White nationalist website. Above pictures of the outgoing president and the Iowa teenager, a headline said, "Click here if you think THEY are not US."

Within months, as debates over election tampering played out in the divided country, the definition of "us" became the subject of intense public conversation. Not long after the gaudy inauguration festivities, America First supporters pressed the new administration to address head-on the question of "Who is a real American?" At an April conference hosted by the revamped National Endowment for the Humanities, four evangelical ministers, dismissing charges of McCarthyism, proclaimed that LGBT citizens were sinners and a threat to the nation. Homeland Security drew up preliminary plans for the deportation of Muslims.

Bureaucracies move slowly at first, but by May 2017, "Go Back Home" had replaced "Lock Her Up" as a frequent chant at weekly rallies. Swayed by such outbursts, the three newly-aligned branches of the federal government started to act. They expanded the Bush-era National Security Entry-Exit Registration System of 2002, so that Muslim Americans, long under surveillance, could be swiftly arrested, interned, and deported. Corrections Corporation of America, the nation's largest private-prison company, doubled its operations to speed the process. C.C.A.'s stock had jumped nearly fifty percent after Trump's election, and its value continued to soar.

Republicans ran op-eds to reassure voters that a Democratic administration had interned persons of Japanese, German, and Italian ancestry during World War II. In August, a Twitter-war erupted over reports from Breitbart News that the government had repatriated Gold Star parents Khizr and Ghazala Khan to Pakistan, as recommended by Richard Spencer's influential National Policy Institute. Debate raged over whether this story, complete with blurry photographs, represented "fake news." Meanwhile, C.C.A. facilities were filling to capacity, so the government turned its prison at Guantánamo, Cuba, into a deportation staging ground.

Even before the Mosque Closure Program was completed in November, the Cabinet turned its attention to a much larger and more difficult question, signaling that 2018 would be the year for deporting Mexican Americans. Leaders in agribusiness and the meatpacking industry objected at first. But leaders in Congress, warmed by continuing public approval, reminded them that the U.S. government had forcibly deported hundreds of thousands of "Hispanics" without due process during Great Depression. Forgotten New England statutes resurfaced to provide precedent for punishing sexual "deviance" with exile.

"Amazing mobilization!" the president tweeted after his State of the Union address. "Forget World War II. We're the greatest generation." But as deportations rose, the editor of Foreign Affairs warned that well-intended government programs had been known to overreach. "They take on a life of their own when sustained by massive funding, interdepartmental cooperation, and Supreme Court support." Despite such cautions, in March Congress approved the "National Security and Unemployment Relief Act" (NSURA), creating a Deportation Authority (DA) in the Homeland Security Administration. As members of the Congressional Freedom Caucus explained, the new law would help to protect jobs for "Real Americans."

When signed into law with massive funding, NSURA made feasible the completion of Hispanic and Latino deportation, moving far beyond undocumented workers to include any family that spoke Spanish as a first or second language. Hard-won success in removing more than sixteen percent of the U.S. population raised administration hopes about tackling the daunting "Black Problem." African Americans represented a smaller portion of the overall population, estimated at around thirteen percent. Still, the Attorney General made clear that deporting African Americans would not be easy, given their long presence and constant race-mixing.

Then a senior policy advisor from Georgia, with a PhD in U.S. history, published several influential op-eds reminding Americans that the "Back to Africa" movement had deep historical roots and had often been supported by Black Americans. Next the Secretary of State, on a visit to Moscow, won a pledge from Russia to provide logistical support. Most importantly, new methods of DNA testing revived and refined the so-called "one-drop rule." In a bipartisan gesture intended to dampen lingering opposition, Congress amended NSURA (Section 17.2, clause 138A) to exempt all Native Americans, plus former presidents and their immediate families, from deportation.

In 2018, Halloween fell on a Wednesday and came at the height of a fevered mid-term election campaign. In New Jersey, pro-deportation forces, anticipating another victory at the polls, staged a raucous torch-light parade, marching across the George Washington Bridge for a rally in New York City. Some wore Klan hoods and chanted "Make American White Again." In New York Harbor, the last of hundreds of huge container ships, rented by the DA from Korean logistics companies, pushed past the Statue of Liberty into the Atlantic, carrying thousands of not-quite-Americans to ports in West Africa, Latin America, and Siberia.

The next evening, hundreds of Jewish Americans raised a makeshift poster of Lady Liberty outside Trump Tower and staged a silent vigil. Some lit candles; others held up copies of Philip Roth's novel The Plot Against America while opponents across Fifth Avenue chanted "Go Back Home!" While covering the clash, one reporter observed police officers arguing among themselves; his story hinted that ethnic tensions in the NYPD offered a sign of things to come. Weeks later, federal agents staged a Thanksgiving Day sweep at nearby Ellis Island, confiscating aging files and electronic databases from the island's cavernous Visitor Center.

For years, tour guides at Ellis Island had informed visitors that "close to 40 percent of all current U.S. citizens" could trace at least one ancestor to that spot. But now the immigrant arrival records, once publically searchable at www.libertyellisfoundation.org/, had been confiscated. "This seems an ominous sign," wrote the cautious Washington Post, which had given scant coverage to the racial deportations that steadily hollowed out the American work force. Similar document sweeps began on the West Coast, aimed at Asian Americans. In a plaintive letter to the Los Angeles Times, a UCLA professor asked, "Haven't we been here before?"

By this point, according to Stenmark's reconstruction of events, few could deny the feasibility and effectiveness of the mass removals. Property confiscations by the DA offered a robust new stream of government revenue, so deportations had to continue. Covertly, the DA also increased its budget by selling expensive indulgences to individuals and families. Before long, only the wealthiest families could afford deportation exemptions, given the collapsing economy. But by then the DA had become an unmanageable force with overwhelming momentum. It had swallowed money and resources dedicated to Homeland Security, and it had nearly absorbed the Defense Department, taking over much of the Pentagon.

The government kept monthly deportation records secret, so estimates of overall removals varied widely. However, an underground newspaper in Atlanta speculated that the country had already lost well over half its people. Unity among White Christian Americans, so impressive just two years earlier, had started to fracture in new and significant ways. Deportations of patriotic families, even those with papers from the DAR and the VFW, had already begun. High-level debates over who should be next grew increasingly heated. Notre Dame, no longer able to recruit Black athletes, cancelled all athletics and committed its dwindling resources to defending the country's remaining Catholics as exemplary citizens.

Far too late, on January 7, 2019, the Wall Street Journal reported on a massive, "perhaps irreversible" decline in U.S. production. Days later, a Chicago Tribune headline was more forthright: "Country's Economy Entering Unforeseen Death Spiral." Silicon Valley experts apologized for brashly predicting that automation could compensate for the loss of over one hundred million workers. Spin doctors tried, but failed, to blame food shortages and chain retail closures on continuing turmoil in the Middle East. As libraries and book shops shut down, remnants of New York's once-powerful publishing industry recycled previous hits in a final bid to stave off devastation.

Most notably, in February, Viking Press reissued anthropologist Jared Diamond's 2005 bestseller, Collapse: How Societies Choose to Fail or Succeed, putting an image of Mr. Trump's Mar-a-Lago Resort on the cover. Diamond was born in Boston in 1937 and had trained at Harvard as a physiologist. He then worked as an ornithologist in New Guinea, later becoming a leading environmental historian and renowned author. But his parents both came from East European Jewish families, so in 2018 he had elected to leave the U.S. for Stockholm. That was where Stenmark found him several years later. She interviewed the octogenarian for her essay, and she included a photograph of him, his Ahab-like beard white with age.

According to her account, Professor Diamond, lively and thoughtful as ever, was intrigued by her own research. He chuckled when he heard that, early in 2019, a number of the remaining American computer users had obsessed over his 2008 TED Talk. He recalled that in the lecture, he had asked pointedly: "What can we learn from the past that would help us avoid declining or collapsing in the way that so many past societies have?" But his reminders about sudden cultural collapse in Easter Island and Iron Age Greenland were revived too late. By June 2019, internet access in the U.S. had stopped entirely, and Viking no longer had paper to print books.

Seated in Diamond's Stockholm apartment, Stenmark discussed the outline of her forthcoming article. She explained how the U.S. Cabinet had divided bitterly early in 2019, less over economic strategy than over ethnic priorities. The President tried to restore unity with a reminder that he had once lobbied hard, if unsuccessfully, to have a huge statue of Christopher Columbus erected in New York, but it was too late. Within weeks, competing agencies had drawn up differing priority lists, often falling back on charts of preferred European nationalities compiled for the Johnson-Reed immigration restriction law of 1924.

In Washington, DC, a street vender sold his last copy of Clinton Stoddard Burr's 1922 bestseller, America's Race Heritage: An Account of the Diffusion of Ancestral Stocks in the United States During Three Centuries of National Expansion and a Discussion of its Significance. In the once-placid suburbs, deportations mushroomed and disunity escalated. Prayer breakfasts and online petitions proved of no avail. In early July, on what had once been Independence Day, the remaining reporter at the St. Louis Post Dispatch scribbled out the paper's last editorial. "This whole region," he wrote for a non-existent readership, "and others elsewhere so far as I can tell, is now pretty much empty."

"Frankly," Diamond told his visitor, "I had thought the American collapse would come more slowly, more like Rome. But what you are describing does not surprise me; social science can rarely predict all the variables." He was particularly interested to hear of the research trip Stenmark and her husband had made to the United States late in 2020. By then, the country's population had crashed to below four million. Amazingly, Native Americans, less than one percent of the U.S. population a decade earlier, had assumed majority status. Diamond chuckled again— "So I suppose the Dakota Pipeline controversy belongs in the past…."

"I'm getting to that," Stenmark replied in her excellent English, readjusting her miniature Scandinavian tape recorder. But first, she described her visit to Iowa City's West High School, used as a polling place four years earlier; grass was growing in sidewalk cracks and weeds covered the football field. Then she showed Diamond her pictures of vacant buildings and crumbling streets across the Midwest. The cellphone images resembled portraits of urban decay that had stirred partisan emotions during the 1916 presidential campaign—only worse.

As the days grew cold, Stenmark said, she and her husband had made their way north to Standing Rock, near what had recently been Bismarck, North Dakota. Flipping through more photos, she showed the aging scholar how they had camped out in fresh snow near the still-flowing Missouri River. "It's easy if you grew up in Sweden," she explained. Then she scrolled to striking images of what they had come to see. Thousands of Native Americans from across North America had gathered there, seated around a series of communal campfires, to discuss what needed to be done next. "Yes," Professor Diamond said, leaning forward and tapping the screen. "Tell me more about that."

Peter H. Wood is an emeritus professor of History at Duke University and a gourd grower now living in Colorado. He continues to write about African American history and long-hidden aspects of the Southern Past.