The Southern Border Poses Terrorism Risks. Homegrown Threats Still Loom Larger.

Recent reporting and opinion articles have raised fears of illegal immigrants crossing the southern border to commit terrorist attacks in the United States on behalf of foreign actors. “The reality is that [President Joe Biden’s] open border is the gravest terrorist threat to the homeland in years,” Senator Tom Cotton (R-AR), for instance, wrote in a Fox article commemorating the twenty-second anniversary of the 9/11 attacks. The comment followed an August news piece in CNN that revealed more than a dozen Uzbek migrants had sought asylum at the southern border, having “traveled with the help of a smuggler with ties to ISIS.”

Those arguments highlighting the threat of terrorist attacks by illegal immigrants overlook three important points of context. First, although such fears can never be completely dismissed, to date they have been mostly hypothetical, as there is scant evidence that illegal immigrants have committed acts of terrorism in the United States. For instance, of the 3,203 offenders in the University of Maryland’s Profiles of Individual Radicalization in the United States dataset, only nineteen (less than 0.6 percent) are listed as “Undocumented Resident.” Most modern acts of American terrorism directed or inspired by foreign terrorist organizations—such as ISIS-inspired attacks in the cities of San Bernardino, Orlando, and New York between 2015 and 2017—are instead committed by “homegrown” legal immigrants or U.S. citizens. This was in fact a deliberate strategy pursued by groups such as the self-proclaimed Islamic State, which calculated—correctly—that it would be far easier to inspire lone actors in the United States than attempt to send operatives into the country. As the Pulse nightclub in Orlando can attest, lone American jihadists can cause plenty of damage without needing to be smuggled across the border. Meanwhile, each of the 9/11 attackers flew into U.S. ports of entry and were in the country legally (albeit with two having outstayed their visas).

Second, fear of illegal immigrants committing acts of terrorism is not entirely unfounded, but it has previously manifested in unexpected ways. In recent years, the most high-profile terrorism incidents involving illegal immigrants have in fact both been perpetrated by Canadian far-right extremists—an anti-government extremist who attempted to attack Speaker of the House Nancy Pelosi (D-CA) in the build-up to the 2022 midterms, and a neo-Nazi who crossed the northern border and joined a white supremacist terrorist organization known as “The Base” in 2020, planning to attack a gun rights rally in Richmond.

In the former attack, the would-be murderer had legally entered the United States as a temporary visitor through the San Ysidro port of entry in 2008, then outstayed his legally permitted stay. The latter incident, conversely, involved perhaps precisely the scenario many now fear at the southern border—an international terrorist organization deliberately smuggling an operative across a U.S. border with the intention to commit a significant act of terrorism against civilians. Of note, the Base conforms to the so-called accelerationist strategy of violent extremism, which seeks to conduct random acts of violence in order to accelerate the onset of an apocalyptic civil war. This far-right attack, accordingly, aimed to kill Second Amendment proponents in order to spark a broader conflagration between rallygoers and police in Richmond.

And finally, immigration does lead to a rise in terrorism, but—again perhaps counterintuitively—this violence has been largely white supremacist in nature, not jihadist, with data analysis from the University of Pennsylvania’s Richard J. McAlexander suggesting “there is little evidence to support the common claim that letting in more immigrants means letting in more terrorists.” Instead, inflammatory rhetoric against immigrants contributes to the white supremacist “Great Replacement” theory, which claims that Jews and Marxists are orchestrating a deliberate replacement of white people in Western countries, operationalized through immigration and minority political power. The theory has directly led to catastrophic white supremacist violence in communities such as Pittsburgh, El Paso, Buffalo, and Jacksonville over the past five years.

The Pittsburgh terrorist, who murdered eleven worshippers at the Tree of Life synagogue in October 2018, directly cited immigration at the southern border as a central inspiration for his attack. “[Hebrew Immigrant Aid Society] likes to bring invaders in that kill our people,” he wrote on far-right social media site Gab. “I can’t sit by and watch my people get slaughtered. Screw your optics, I’m going in.” The El Paso terrorist, who murdered twenty-three primarily Latino shoppers at a Walmart in August 2019, having traveled to the border town explicitly in search of immigrants, was arguably even more blunt: “This attack is a response to the Hispanic invasion of Texas.” White supremacist terrorists have killed more Americans than jihadists since 9/11—and pose an imminent threat not just to minority communities, but also the federal government as well as the Republican Party.

This data suggests that the issues of immigration and terrorism are indeed linked, but the problem is in fact far more nuanced than some commentators suggest. There are, then, at least three conclusions from the preceding analysis. First, the United States should, indeed, carefully watch for terrorism suspects entering the country, but the greatest threats will likely attempt to enter legally—or were born here. Second, the United States’ northern border at least historically has proven to be a comparable source of documented instances of politically motivated violence as the southern border, which consumes disproportionate attention in this febrile, polarized political environment. And third, a broader effort should be undertaken to counter the dehumanization of immigrants in American political rhetoric and finally enact much-needed immigration law reforms that would make the border less of a partisan, political flashpoint.

A porous southern border does provide an opportunity for jihadist terrorist organizations to send operatives to the United States. But for now, the most serious terrorist danger still comes from lone-actor white supremacists, radicalized online here inside the United States, attacking soft targets using firearms—as displayed to such heartbreaking effect just weeks ago in Jacksonville.

This post was written for the Council on Foreign Relations’ Renewing America initiative—an effort established on the premise that for the United States to succeed, it must fortify the political, economic, and societal foundations fundamental to its national security and international influence. Renewing America evaluates nine critical domestic issues that shape the ability of the United States to navigate a demanding, competitive, and dangerous world. For more Renewing America resources, visit https://www.cfr.org/programs/renewing-america and follow the initiative on Twitter @RenewingAmerica.