Americans like to forget we ever had an empire or to claim that, if we did, we never really wanted one. But the momentum of Manifest Destiny made us an imperial power. It carried us well beyond the shores of the continent we seized from its original aboriginal and Mexican owners. The Monroe Doctrine proclaimed an American sphere of influence in the Western Hemisphere. But the American empire was never limited to that sphere.
In 1854, the United States deployed U.S. Marines to China and Japan, where they imposed our first treaty ports. Somewhat like Guantánamo, these were places in foreign countries where our law, not theirs, prevailed, whether they liked it or not. Also in 1854, U.S. gunboats began to sail up and down the Yangtze River (the jugular vein of China), a practice that ended only in 1941, when Japan as well as the Chinese went after us.