What was the name of the policy created in 1947 and used by the americans against communism?

The answer is: That´s the Truman Doctrine.

Explanation:

The Truman Doctrine is  a foreign policy conception formulated by president Harry Truman in 1947. It was designed in order to oppose and contain Communist expansion around the world. It was a major development in the US geopolitical strategic thinking. Truman´s diplomatic strategy was a major reorientation of American foreign policy which had traditionally advocated taking distance from regional conflicts and  involvement. The Truman Doctrine says that the US will provide all types of assistance to any nation threatened by internal or external authoritarian forces.

the constitution of the united states gave congress the absolute authority over immigration laws