Why did the United States pursue an isolationist policy toward Europe for most of its history? Why did Americans abandon isolationism in the twentieth century?
The roots of American isolationism lie deep in the nation's colonial past. The first settlers, separated from Europe by distance and time, were compelled by necessity to develop their own patterns of behavior and thought, and ultimately their own nation. The relative peace, freedom, and economic opportunity that the New World offered contrasted quite glaringly with the constant warfare, social and economic inequity, religious intolerance, and political oppression that characterized the Old World. Reinforced by the Declaration of Independence and the Constitution, Americans quite easily came to regard themselves as morally and politically superior to Europeans. This sense of superiority provided additional justification for the desire most Americans possessed to themselves as much as possible Europe's problems.
American isolationism was also encouraged by George Washington's 1796 Farewell Address. In it, the first president urged his fellow citizens to avoid permanent alliances in order to concentrate their energy on developing the young nation. James Monroe, in his declaration of 1823, reinforced the advice of the Farewell Address by stating that the United States had no intention to interfere in Europe's affairs and, in turn, would tolerate no further European colonization in the New World.
Yet while the first presidents regarded American nonentanglement in Europe's political problems as essential to the welfare of the young nation, they also realized that its peace, prosperity, and independence were to a great extent dependent on the existence of a balance of power in Europe. For this reason, they did not exclude the possibility of American participation in temporary alliances or military action designed to maintain the European balance of power. Indeed, the effectiveness of the Monroe Doctrine throughout most of the nineteenth century was based on the support the British navy gave it, for until late in the century America's navy could not enforce it. Nor did the first presidents think that America's isolation from Europe's political affairs need be permanent. One day, they foresaw, America would be sufficiently strong to play a major role in the affairs of the world as well as in Europe.