Containment was a United States policy using military, economic, and diplomatic strategies to temper the spread of communism, enhance America’s security and influence abroad, and prevent a "domino effect". A component of the Cold War, this policy was a response to a series of moves by the Soviet Union to expand communist influence in Eastern Europe, China, Korea, and Vietnam. It represented a middle-ground position between appeasement and rollback. The point of the Containment Policy was for the United States during the Cold War to keep Communism from spreading. Also if they failed then the domino effect would occur and eventually, more and more countries would fall to Communism. This is the reason the USA fought in the Vietnam War and the Korean War. The role of the policy was major. Both sides fought for and against it. This caused the sides to go to war. Basically this policy started the war. Therefor you can say that the policy had a huge role.
Another implication would be that Containment was the reason why the U.S entered the war.
Another implication would be that Containment was the reason why the U.S entered the war.