Beyond being a historical myth, is the rallying cry of the “liberal international order” likely to impress voters?

Foreign policy experts are betting on a fantasy, one mostly confined to the Acela Express. Those experts who seek to shape public opinion, to judge by their columns, interviews and tweets, have faced this responsibility only halfway. The president could not be luckier. Little short of catastrophe will vindicate his critics. Mr. Trump can clear their low bar by being unspectacularly awful. More important, the current debate does nothing to forge a future foreign policy that improves on what preceded Mr. Trump’s election. Far from devising alternatives, experts are shutting down needed debate by collapsing America’s interests into an abstract “order.” They increasingly resemble the “globalists” whom candidate Trump derided.

The irony is, Mr. Trump was wrong. Policymakers have always put American interests first, adjusting (or defying) the rules accordingly. In 1945, Harry Truman met Winston Churchill and Josef Stalin in war-torn Potsdam, Germany. If this was the moment of creation of the “liberal international order,” as today’s commentators maintain, Truman did not know it. (Neither he nor his advisers used the phrase.) The frustrated president wrote to his wife, Bess, “I have to make it perfectly plain to them at least once a day that so far as this President is concerned Santa Claus is dead and that my first interest is U.S.A.”

Truman understood what Mr. Trump’s critics implicitly deny: the possibility that American power can come at the expense of others. The foreign policy establishment clings to the fiction that what’s good for America is necessarily good for the world. They condemn Mr. Trump’s tariffs as an unthinkable breach even though the United States has employed protectionist measures throughout history. They pretend that Mr. Trump, having vowed to take things from the world, must be diminishing American power when he seeks to expand it. Mr. Trump’s actions may not have their intended effect, but the most logical and cutting response isn’t that he is weakening America but that he’s trying to strengthen it in a way we should not want. His outpouring of militarism and chauvinism may or may not reduce the United States’ influence. It does, however, threaten to turn the world’s sole superpower into an unabashed purveyor of violence and exploitation.

Let’s call Mr. Trump’s vision what it is: radical American imperialism. He does not so much break with tradition as bring forward some of its most retrograde but persistent elements. Recognizing this is the start of an honest conversation about the Trump administration and America’s role in a changing world. So far, however, the right has come closer to grasping this point than the left or the center. Mr. Trump and his supporters do identify a conflict (indeed, almost endless conflict) between America’s interests and the world’s. As Rush Limbaugh recently put it, Mr. Trump wants to restore the “primacy of the United States,” whereas his critics think “American leadership should preside over the weakening of America.” The point is perverse, but it is coherent. Fearing decline, the Trumpian right seeks to get tough with the world and take all it can.

Mr. Trump’s challenge can be met. As distributional conflicts surge in domestic politics, they are surging in foreign policy, too — and those who ignore them lose out to those who inflate them. Citizens seeking a better foreign policy ought to be engaged, not ignored. But recent events cast doubt on whether our current crop of experts is up to the job.

Democracy requires experts but it also requires something from them: that they facilitate public debate and respect the ultimate power of the electorate to set the aims of the nation. By rallying behind the lowest common denominator of “anything but Trump,” they are disengaging the public’s discontent, pulling up the drawbridge until the next election. In that sense, Donald Trump is not the only one who might be called an isolationist.