What declaration warned against interference in the America's?

The Monroe Doctrine, proclaimed by President James Monroe in 1823, warned European nations against further colonization or interference in the affairs of the Americas. It asserted that any attempt by a European power to control or influence nations in the Western Hemisphere would be viewed as a hostile act against the United States. This doctrine effectively established a policy of American dominance in the region and laid the groundwork for future U.S. foreign policy in the Americas.