Which american policy was meant to keep european countries from getting
involved in north and south america?

One of the most iconic American policy in the American history, that was meant to keep Europeans countries from getting involved in North and South America was the Monroe Doctrine.

Explanation:

It is considered as a “cornerstone of U.S. foreign policy”. It was enunciated by James Monroe. According to this doctrine, the Old World and the New world had different systems and should remained as two distinct spheres. In this doctrine Monroe mad four basic points:

(A) the U.S. would not interfere in the internal affairs of wars between the European powers.

(B) US would not interfere with the existing colonies in the Western Hemisphere.

(C) the western hemisphere was closed for future colonisation.

(D) any sort of attempt to oppress or control any nation in the Western Hemisphere would be consider as an act of hostility act against the United States.