Americans themselves regarded their famed niceness as the cornerstone of a democratic personality. The actress and writer Kate Field remarked in 1873: “To try to please everybody, is democratic; to be indifferent to everybody is aristocratic: consequently, Americans, men and women, are the best bred people in the world.” As a refreshing alternative to European stuffiness, American niceness conveys democratic informality while sustaining the myth of American exceptionalism: Americans are not just nice but the nicest people on earth. As Walt Whitman once put it, Americans are “the peaceablest and most good-natured race in the world.”

Since the 19th century, Americans’ belief in our own niceness has never wavered. Yet even then, American niceness obscured a tendency to refuse accountability for aggression and offense — and even unspeakable cruelty.