Answer:
The main idea of the Monroe Doctrine was to assert the United States' opposition to European colonialism and intervention in the Western Hemisphere. The doctrine, articulated by President James Monroe in 1823, stated that any attempt by European powers to colonize or interfere with the affairs of independent nations in the Americas would be seen as a threat to the United States and would require a response. The doctrine helped establish the United States as a dominant power in the Western Hemisphere and set the stage for American expansionism in the 19th and 20th centuries.
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