The entire concept of “American exceptionalism” is controversial. Used by both major parties to advance their agendas of the moment, the belief that there’s something distinct and unique about America has been present for hundreds of years. It’s been co-opted by both boosters and detractors to explain away countless features of the U.S. landscape—from our high rates of gun violence and abnormal health care costs to our disdain for authority and penchant for self-reliance. But while American exceptionalism may or may not be real in the political realm, it’s been...