A. It gave Europe the message that the Western Hemisphere was no longer open for colonization.
The Monroe Doctrine said that no European powers will be allowed to colonize the Western Hemisphere because the United States had to fulfill their Manifest Destiny.
Any of these should work
The Founding of the Colonies
French and Indian War
Taxes, Laws, and More Taxes
Protests in Boston
Intolerable Acts
Boston Blockade
