This chapter explores the paradox of American power in two distinct historical periods. The first begins with the nation’s founding and extends through World War I, during which the United States charted a course of unilateral action, avoiding diplomatic entanglements with the great powers of Europe while building an industrial economy that would make the United States a major force in global trade markets. This period witnessed tremendous territorial expansion. In short, with the acquisition of the Louisiana Territory from France, followed by the displacement of Spain from Florida, the subsequent demise of the Spanish empire in Latin America, and the favorable resolution of lingering trade and territorial difference, with Great Britain in the War of 1812, the United States was free to exercise regional hegemony. In 1823, to cement this new state of affairs while discouraging any would-be competitors from intruding upon its sphere of influence, President James Monroe proclaimed the Monroe Doctrine, politically separating the United States from Europe, and declaring future colonization in the Western Hemisphere a threat to U.S. national security.

The second period covers the conduct of U.S. foreign policy once the country became a great power in the 20th century. The United States began the century in the midst of a struggle to colonize the Philippines and then asserted hegemonic control over Central America. Emerging from the world wars with unprecedented military strength and economic clout, U.S. leaders then became engulfed in the Cold War with the Soviet Union and other communist states. The Soviet Union’s collapse in 1991 left the United States in the position of unprecedented global primacy. Even so, maintaining this status proved more difficult than expected as regional conflicts and civil wars ignited in many parts of the world. The United States found that even after the end of the Cold War, ethnic and religious conflicts, along with global terrorism, present problems for the “new world order.”