Throughout history, American presidents have declared it their job to protect and advance the interests of the United States and its citizens. President Trump has shoehorned that wholesome, uncontroversial idea into a narrow-minded, exclusionary governing platform that’s likely to alienate much of the world while hurting the very people whose cause he claims to uphold.

In his campaign, his Inaugural Address and, most recently, his speech to Congress, Mr. Trump has proudly embraced the isolationist “America First” rallying cry from the 1930s while rejecting the internationalism of his predecessors. He has disparaged NATO, an alliance that has helped keep the peace in Europe for more than half a century; cozied up to Russia and its latter-day czar, Vladimir Putin; disdained global solutions to global problems like climate change and the surge of refugees from Syria, Iraq and elsewhere; and declared his intention to upend the international trading system created by the United States and its allies. Nowhere is his cramped vision more evident than in his scapegoating of unauthorized immigrants as criminals and his rejection of the American ideal of welcoming the foreign-born.

A GO-IT-ALONE APPROACH

Of late, Mr. Trump has seemed to back off from some of his views, as in his assertion on Tuesday evening that “we strongly support NATO.” But it is unclear what that will mean in practice, especially since Defense Secretary Jim Mattis repeated Mr. Trump’s threat to “moderate” America’s commitments to NATO if the allies don’t pony up more for defense.

In one breath Mr. Trump tells Congress, “Our allies will find that America is once again ready to lead”; minutes later, he says: “My job is not to represent the world. My job is to represent the United States of America.” No president can claim to represent the world; yet since World War II, all have accepted, even celebrated, America’s unique power and ability to lead in promoting democracy, peace and free markets. The word “democracy” did not appear in Mr. Trump’s speech, something that should have been central to this address. And he said little about working with allies on common interests.