President Trump has brought to the surface a nationalist sensibility that has been latently present in the conservative movement for a long time. In September, he told the United Nations General Assembly that the future belongs to “patriots,” not “globalists.” Trump has also blamed “globalism,” an intricate ecosystem of international treaties, alliances, and organizations, for all manner of domestic ills. “America is governed by Americans,” the president told the U.N., not by unaccountable bureaucrats. European allies in NATO are not “paying their fair share.” Free-trade agreements, in Trump’s telling, have generally been “rip-offs” for workers. The European Union, meanwhile, was set up to “take advantage” of the United States. Trump’s criticisms, like earlier critiques by conservative intellectuals, are not without merit. It is true, for example, that many international agencies have outlived their original rationale...