Many governments must be thinking along the same lines, but few have spelled it out so clearly. Germany did, when Chancellor Angela Merkel said, “The times in which we could rely fully on others — they are somewhat over.” Now Canada, a country tightly bound to its neighbor by history, alliance and the longest border in the world, has declared the need to recognize that the United States is relinquishing its role as the “indispensable nation.”

“The fact that our friend and ally has come to question the very worth of its mantle of global leadership puts into sharper focus the need for the rest of us to set our own clear and sovereign course,” Canada’s foreign minister, Chrystia Freeland, told her Parliament this month.

Ms. Freeland never mentioned Donald Trump. That wouldn’t be diplomatic. But every line of her speech before a silent House of Commons was clearly about a world order thrown into crisis as President Trump scoffs at trade agreements, hectors allies, rips up the landmark Paris climate accord and otherwise demonstrates disdain for anything that isn’t “America First.” Canada’s course, Ms. Freeland said, would be the opposite of Canada First; it would be “the renewal, indeed the strengthening, of the postwar multilateral order.”