In less than two weeks, President Donald Trump has upended America’s long-standing role in the world.

At the United Nations on Monday, in the same hall where U.S. diplomats for decades confronted their Russian counterparts on behalf of the “free world,” Washington’s envoy joined Moscow in voting against a resolution condemning Russia’s invasion of Ukraine. 

The vote followed a week in which President Trump seemed to side with Russia against Ukraine, announcing plans to…