“A cry for racial justice some 400 years in the making moves us,” Biden said, a gesture to the protests that swept the country over the summer. “A cry that can’t be any more desperate or any more clear. And now a rise of political extremism, white supremacy, domestic terrorism that we must confront and we will defeat.”

He went on: “I know the forces that divide us are deep and they are real. But I also know they are not new. Our history has been a constant struggle between the American ideal that we all are created equal, and the harsh, ugly reality that racism, nativism, fear and demonization have long torn us apart.”

Biden has said he felt compelled to run for president after Trump appeared to defend the participants in the 2017 white-supremacist rally in Charlottesville. That rage then found a troubling echo in the storming of the U.S. Capitol by far-right extremists just two weeks ago. Some of the rioters who sought to violently overturn the electoral college count certifying Biden’s win waved Confederate flags and sported slogans cheering the Holocaust. Biden branded them “domestic terrorists.”

U.S. investigators say the Jan. 6 pro-Trump rally that preceded the storming of the Capitol was attended by known white supremacists, some of whom were already on FBI terrorism watch lists. Nearly 1 in 5 of the more than 140 defendants charged so far for their alleged involvement in the Capitol attack appear to have served in the military, according to NPR. Ahead of Biden’s inauguration, authorities removed 12 members of the National Guard who had been deployed in Washington after vetting revealed that at least two had possible sympathies or ties to anti-government groups.

In Germany, authorities over the past year also woke up to the threat of white nationalists and neo-Nazis steadily infiltrating the country’s security forces. Last July, the government disbanded an elite military unit because its commandos had suspected far-right ties. “There is an urgent need for action,” Eva Högl, the German parliament’s commissioner for defense, told reporters at the time. “It has been trivialized. It wasn’t taken seriously enough.”

Among those who didn’t take the threat seriously enough were officials in the Trump administration, which appeared to disregard concerns over an emerging set of organized, transnational far-right militant groups. “Our requests to our U.S. counterparts for legal assistance and information exchange in matters of right-wing extremist groups would often be unanswered,” said a European intelligence official, who spoke to my colleagues on the condition of anonymity last summer because the person was not authorized to discuss the issue publicly.

There’s a broad spectrum of far-right extremist behavior that has analysts worried. Beyond the armed militia-style groups training for violence, far-right mobilization has dovetailed with QAnon, a sprawling set of false claims that have coalesced into an extremist ideology that has radicalized its followers. The main underpinning is a belief that Trump is the predestined destroyer of a secret cabal — including Democrats and celebrities — that traffics children for sex and eats them. Biden’s victory, and Trump’s departure, has hardly cooled the fervor among QAnon adherents.

“What we’re seeing is a trend in increasingly bunker-down, apocalyptic language,” Joel Finkelstein, co-founder of the Network Contagion Research Institute, a research group that studies online disinformation, told my colleagues. “It’s gone from [talk of] a revolution to a civilization-ending kind of collapse.”

And it has already spread to Europe, where far-right protests echoing some of the outlandish beliefs of QAnon have flared. “If ever there was a sign that American tech platforms were having an impact on international discourse in a way that has no borders, this is it,” Anna-Sophie Harling, the head of Europe at NewsGuard, a firm that tracks misinformation online, told my colleague Adam Taylor.

“Rather than treating right-wing extremism as isolated incidents parochial to particular countries, it is time to recognize it as a global and evolving phenomenon,” wrote Heather Ashby in Foreign Policy. “If the United States and the international community do not quickly mobilize resources to unite against this threat, they may lose an important chance to stem its spread.” She added that governments and societies needed to invest in long-term media-literacy projects to counter disinformation.

But the question of what can be done is thorny. The United States cannot censor or criminalize certain forms of hate speech the way Europe can, though the Biden administration is expected to lean more aggressively on tech companies to deal with disinformation and the spread of extremism on their social media networks.

Many policy wonks and lawmakers in Washington have called for a top-down approach to domestic terrorism akin to what was marshaled against Islamist extremism in the wake of 9/11. That unnerves critics who fear the United States is learning the wrong lessons after years of often heavy-handed counterterrorism policymaking.

“Those critical of passing a domestic terrorism law argue that there are already dozens of federal terrorism crimes, hate crime and organized crime statutes that can be applied to domestic terror acts — it simply comes down to an administration that gives precedence to homeland threats,” according to a Politico report. “And more than 130 civil and human rights groups warned that creating a domestic terrorism charge could be used as a vehicle to racially profile and target marginalized communities.”