The idea that the United States should lead the world, replacing the British Empire, had been advanced by various U.S. leaders and influential citizens since the late 19th century. This ambition was in keeping with age-old aspirations of great states and empires, and also with the trajectory of U.S. history. The U.S. expanded across North America in the 19th century, became an imperial power in Asia in 1899, declared Latin America an exclusive sphere of influence in the early 20th century, and became the foremost global economic power prior to the First World War.
Cold War interventionism, 1945-1990
UNITED STATES FOREIGN POLICY