The Manifest Destiny, Monroe Doctrine and the Expansion of the United States During the 19th and 20th centuries, US foreign policy were based on the Monroe Doctrine and the Manifest Destiny. The Monroe doctrine was the belief the United States should not let Europeans plunder the Western Hemisphere. The Manifest Destiny was the idea that Americans were God-chosen people ordained to establish a model society. These two beliefs pissed off foreign powers, particularly those who still held colonies on North America. The leaders of the United States were letting them know that they have only two choices: leave or face military force. The idea of Manifest Destiny can be referred to the territorial expansion of the United States from the Atlantic