Answer:
There was a domino effect of communism getting spread in the countries of south East Asia.
Step-by-step explanation:
Communism gradually became conceptual for China and it was feared that communism would gain roots gradually in United States; also the cold war was prevalent.
Vietnam is a country which borders China and United states believed that a stratagem that was diplomatic to make Communism spread in America was going on. This made United States to wage a war against Vietnamese.
Tensions between US, China and Soviet Russia established the global framework for hostilities.