The answer is that Khan helps Trump articulate his new, and still not widely understood, brand of American exceptionalism.

As I’ve suggested earlier, “American exceptionalism” is not an enduring set of American values. It’s an enduring method of American contrast, a way of distinguishing the United States from Europe. The nature of that contrast has changed radically over time. Until World War II, many Americans thought that what distinguished the two continents was Europe’s proclivity for war, which the peace-loving, commercial-minded United States, should avoid. After the Russian revolution, Americans often said that what made their country exceptional was its lack a strong socialist or communist movement.

Barack Obama often suggested what made America exceptional was its capacity for inclusion. After recounting his Kansan-Kenyan ancestry, he frequently claimed that, “In no other country is my story even possible.” In 2015, he told British Prime Minister David Cameron that “Our Muslim populations, they feel themselves to be Americans. There is, you know, this incredible process of immigration and assimilation that is part of our tradition that is probably our greatest strength. There are parts of Europe in which that’s not the case, and that’s probably the greatest danger that Europe faces.”

Trump has turned that on its head. Like previous presidents, he defines America in contrast to Europe. But for Trump, what makes America exceptional is not its peacefulness or inclusiveness or resistance to socialism. It is its resistance to globalism. America is the opposite of the European Union. It is the place where borders and national identity remains king. During the Cold War, hawks often said that what distinguished America from Europe was America’s willingness to resist the Kremlin. For Trump, what distinguishes America from Europe is America’s willingness to resist Davos and Turtle Bay.

For Trump and his supporters, globalism kills jobs and it kills people. And it does the latter, in large measure, by allowing Muslims into the West. Keeping America exceptional, therefore, means ensuring that Muslims never gain the same foothold in the U.S. than they’ve gained on the other side of the Atlantic. This idea has obsessed Steve Bannon for years. He’s explained that one of the reasons he opened a Breitbart office in London was to show Americans that “all these Shariah courts were starting under British law.” In December 2015, he warned that if America doesn’t “hit the pause button today … we’re going to be importing at least a couple of million Muslims” per year. In a Fox interview this February about Trump’s travel ban, senior White House aide Stephen Miller brought up Europe unprompted. “The most important thing to discuss right now,” he said, “is how do we keep this country from falling into the same trap as happened to parts of Europe to places like Germany, to places like France, where you have a permanent intergenerational problem of Islamic radicalism that becomes a routine feature of life in those countries, a new normal. How do we keep that from happening in America?”