In the fall of 1990—around the time U.S. troops arrived in Saudi Arabia, enraging Osama bin Laden—the historian Bernard Lewis sounded an alarm in The Atlantic about brewing anti-Americanism in the Muslim world. “[W]e are facing a mood and a movement far transcending the level of issues and policies and the governments that pursue them,” he wrote. “This is no less than a clash of civilizations—the perhaps irrational but surely historic reaction of an ancient rival against our Judeo-Christian heritage, our secular present, and the worldwide expansion of both. It is crucially important that we...