New British Prime Minister Boris Johnson is eager to negotiate a trade deal with the United States. But at what price? Other countries negotiating with the U.S.—China, Japan and the U.K.’s neighbors in the European Union—all seem to be stalling in the hope that President Donald Trump won’t be reelected.

Mass international tourism, like the free flow of goods and services, has become a hallmark of globalization. This is neither accidental nor trivial. The ability to travel the world is a function of international cooperation. It is also a force for global understanding at a time of resurgent nationalism.