After World War II, America emerged as a global superpower. To maintain this status, policymakers created laws that promoted US intervention in the affairs of other countries.
Two examples of this would be the Truman Doctrine (1948) and the Marshall Plan(1949). These two laws give a significant amount of financial assistance to countries in Europe ($400 million for Truman Doctrine and $13 billion for Marshall Plan) in order to ensure that they do not fall under the influence of the communist Soviet Union. This interventionist policy also helped the US to make allies.
Along with this, the US got involved in other countries civil affairs to ensure that communism did not spread to capitalist countries. Two examples of this include the Korean and Vietnam War.
It is clear that after World War II policymakers focused on extending America's influence and policies to other nations around the world.