After Vietnam won independence from French rule in 1954, civil war broke out between North and South Vietnam. Why did the United States involve itself in the conflict?

The Vietnam War was a long, costly and divisive conflict that pitted the communist government of North Vietnam against South Vietnam and its principal ally, the United States. ... of the Indochinese peninsula, had been under French colonial rule since the 19th ... the Viet Minh, or the League for the Independence of Vietnam.There was an effect of Vietnam being divided into two parts in 1954 Vietnam treaty. It is in this separation that North part of Vietnam rebuild nationally, recovered from wounds of war and got ready to prepare for anticipated war.1954 in the Vietnam War. ... The United States was concerned and worried that a French military defeat in Vietnam would result in the spread of communism to all the countries of Southeast Asia—the domino theory—and was looking for means of aiding the French without committing American troops to the war.