As an American living in Britain for the past decade, I’ve had a front-row seat to two dysfunctional democracies hell-bent on embarrassing themselves. President Donald Trump warned that a hurricane was “one of the wettest we’ve ever seen, from the standpoint of water.” Prime Minister Liz Truss failed to outlast a lettuce at Downing Street. These years have not inspired confidence in democracy.

In Britain and the United States—and across most faltering Western democracies—this democratic dysfunction is routinely chalked up to a catchall culprit: polarization. The reason our democracies are decaying, we’re often told, is that we’re more divided than ever before. And that’s true: Polarization is worsening. Debates over Brexit and Trump tore citizenries—and families—apart.

But Britain’s and America’s democratic woes are not at all the same. The problems in American democracy are worse. That’s because a particularly insidious disease has infected the core of its political system, one that is not present to the same degree in other rich democracies: extreme conspiracism. Other countries, including the U.K., have polarization. America has irrational polarization, in which one political party has fallen under the spell of conspiratorial thinking. Polarization plus this conspiracist tendency risks turning run-of-the-mill democratic dysfunction into a democratic death spiral. The battle for American democracy will be a battle over reality.

Within the modern GOP, conspiracy theories—about stolen elections, satanic cults, or “deep state” cover-ups—have replaced policy ideas as a rallying cry for Trump’s MAGA base. Trump’s disciples have developed an encyclopedic knowledge of a dizzying cast of characters, along with a series of code words for alleged cover-ups. They rattle off their accepted wisdom about conspiracies that most people have never heard of, such as “Italygate,” the absurd notion that the U.S. embassy in Rome, in conjunction with the Vatican, used satellites to rig the 2020 presidential election.

In Britain, far fewer people believe in conspiracy theories. According to YouGov polling, a third of Americans believe that a small group of people secretly runs the world, while just 18 percent believe the same in the United Kingdom. Similarly, 9 percent of Americans think COVID-19 is a fake disease. In Britain, that figure is just 3 percent. Seventeen percent of Americans agree with the statement that “a secret group of Satan-worshipping pedophiles has taken control of parts of the U.S. Government and mainstream U.S. media,” compared with 8 percent of Britons.

What’s really troubling about this political moment in America, though, is not merely the spread of conspiratorial thinking in the general population. It’s also that the delusions have infected the mainstream political leadership. The crackpots have come to Congress.

When Kevin McCarthy finally became speaker of the House this week, one of the first photos to circulate was a selfie taken with Republican Representative Marjorie Taylor Greene, a former QAnon believer who once blamed a wildfire on Jewish space lasers.