The importance of the Monroe Doctrine to European countries was established in the United States as what?

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.

answer; ///i believe the correct answer is john marshall;

i just did something on this guy a few days a go give me two minutes to find it in my notes.