Answer:
Because they wanted to combat the communist influence in Asia.
Explanation:
Communism and Capitalism were enemies after World War II. Allies during the war times, the conflicts aftermatch was the split of Europe (and, somehow, the world itself) into two influence zones, supported by the United States and the Soviet Union. In the case of the soviets, it's the zone of influence was Eastern Europe, and part of Asia, which includes China (which became a Communist regime in 1949), the Korean peninsula, and Vietnam. It was an enormous influence, and the Americans were afraid that, once the Soviet Union owning all these countries, they could be stronger than the United States, and because of that, win the war (the Cold War, in this case). In the case of Vietnam, it was split into two territories, just like the entire world if we say so. In the north, the communist. In the south, the capitalist. But what afraid America most it was that South Vietnam wanted to be united with the north part, creating a communist country. The United States couldn't allow this, and then, they started the interference on the territory. However, the main reason to do that is that if they succeed in the fight, it was an open road to the Korean peninsula, and to create a capitalist influence zone there.
