History has not dealt kindly with imperial ambitions, and America, however benevolent her intent, cannot hope to be an exception. Something remarkable happened on the eve of the U.S. invasion of Iraq. Commentators began to declare, in somewhat exultant tones, that America had at last become a true empire. America was of course also a benevolent empire, they insisted, but that nod to altruistic tradition could not hide their excitement that America had at last joined the greatest empires of the past. Implicit in these giddy declarations was the assumption that empire was an exalted state of power and...