The great American hope is that the country can win a final victory over dangerous enemies and then never think about the external world ever again. When that hope is balked, when the Armistice does not deliver eternal peace and self-balancing security, many Americans blame themselves: If the external world is recalcitrant, America must have provoked it. Self-accusation is as American as self-assertion—and as based on illusions. America has acted as it has over the past century not because it is so good or so bad, but because it is so rich, so visible, and so strong. America’s strength sways world politics even when it is not exerted: Any aggressive illiberal power must fear the United States as the ultimate potential check on its aspirations. So it was with Germany in 1917. So it is with Iran today.