Q. What do you call someone who speaks only one language?

A. An American.

It’s an old joke, but it still works. In fact, I’m monolingual myself, even though my academic work was largely focused on international trade and finance. In my defense, the great bulk of global economic research is published in English; and in general, Americans’ lack of language skills is less important than their insularity, their relative unfamiliarity with what happens and how things work in other nations.

Other countries, especially wealthy ones that more or less match the United States in technological development and general ability to get things done, are a sort of mirror that helps us see ourselves more clearly. Yet many Americans, even supposedly…