How did America change following the Monroe Doctrine?

Although initially disregarded by the great powers of Europe, the Monroe Doctrine became a mainstay of U.S. foreign policy. In 1823 U.S. President James Monroe proclaimed the U.S. protector of the Western Hemisphere by forbidding European powers from colonizing additional territories in the Americas.

it affected it because the kingdoms (with trade) slowly got richer and richer.

(b) britain had a much larger navy than the u.s.

(d) the u.s. had a small army compared to britain.