Is the Monroe Doctrine a US foreign policy? Why?

Yes, the Monroe Doctrine is a U. S. foreign policy.

Explanation:

Although initially disregarded by the great powers of Europe, the Monroe Doctrine became a mainstay of the U. S. Foreign Policy. In 1823, United States President James Monroe proclaimed the protector of the united state of the Western Hemisphere by forbidding European powers from colonizing additional territories in America.