Which important issue did the Monroe Doctrine address in relation to European powers?

The Monroe Doctrine addressed the issue of colonial expansion by asserting that the Americas were no longer open to European colonization and that any attempts by European powers to extend their influence into the Western Hemisphere would be viewed as acts of aggression against the United States. This policy, articulated by President James Monroe in 1823, was aimed particularly at deterring European nations from establishing new colonies or interfering in the affairs of independent nations in the Americas.

The doctrine established a clear boundary in the geopolitical landscape of the time, promoting the idea that the United States had a vested interest in the stability and autonomy of the nations within this hemisphere. It was significant in shaping U.S. foreign policy and reflected the growing sense of nationalism and confidence in American sovereignty during the early 19th century.