"[T]he occasion has been judged proper for asserting, as a principle in which the rights and interests of the United States are involved, that the American continents, by the free and independent condition which they have assumed and maintain, are henceforth not to be considered as subjects for future colonization by any European powers." —President James Monroe, Annual Message to Congress, 1823 To what occasion is Monroe referring?

A. The withdrawal of Spain and Portugal from South America
B. The failed attempt by Russia at preventing American trade with Asia
C. The issuance of a threat by France to reclaim part of the Louisiana Purchase
D. The deployment of American troops to Mexico to fight for the Texas territory