Who said no more colonies could be started in Americas?

The statement that no more colonies could be started in the Americas was made by President James Monroe in his Monroe Doctrine, articulated in 1823. This doctrine asserted that the Americas were closed to further European colonization and intervention, emphasizing that any such efforts would be viewed as acts of aggression against the United States. The Monroe Doctrine aimed to protect the sovereignty of newly independent nations in Latin America and establish a sphere of influence for the U.S. in the Western Hemisphere.