Why was it that the USA intervened in Vietnam between 1954 and 1963?

Vietnam, as a part of Indochina, had been under French Control since 1887. After the withdrawal of French in 1954, the US intervened in the Vietnam War due to the lessons from China, Korea and domino theory, weaknesses of South Vietnam and Vietcong.
The US saw China and Korea fell as dominoes in 1949 and 1953. They were not prepared to see another falling domino. Not only this, if Vietnam fell, the countries around will be influenced in the mean time, including Cambodia, Laos, Burma, Thailand, Malaysia and even India and Indonesia. The Geneva Agreements in 1954 has divided Vietnam between…