With colonial power in 1898, the United States' role in the world changed to that of isolation and expansion. There are three main US ideologies that contributed to the change of the role of America in the world, Manifest Destiny, the Monroe Doctrine and the Open Door Policy. From the time of President Washington, Americans have believed in the theory of manifest destiny. "Manifest Destiny was the idea that it was the obvious destiny of the United States to expand on the continent of North America." (http://historicaltextarchive.com/sections.php? op=viewarticle&artid=297).
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