American scholars and journalists have long debated their country’s national identity. Twenty years ago, the Harvard political scientist Samuel P. Huntington published his book, Who Are We? America’s Great Debate, a title typical of this soul-searching. Huntington made much in this book, written in the shadow of the 9/11 attacks, of the legacy of the American founding fathers, and the “American Creed” initially formulated by Thomas Jefferson, the product of a distinct Anglo-Protestant culture. Huntington identified key elements of that culture: “the English language; Christianity; religious commitment; English concepts of the rule of law, the responsibility of rulers, the rights...