yehudayona,
The Vietnam War ended with the signing of the Paris Peace Accords in January of 1973. The US then pulled out their entire fighting force and the vast bulk of their people. When it became clear that Nixon was going down due to Watergate, Congress passed legislation forbidding the President from intervening in Vietnam without Congress’ advance approval. Seeing this, and after having time to recover from military losses, North Vietnam broke the Peace Accords over two years after signing them and re-invaded South Vietnam in 1975 (the Viet Cong started fighting again 1974).
Without Nixon and US military help South Vietnam fell relatively quickly to the North and Ford ordered the evacuation of US personnel in South Vietnam.
If not for Watergate, history would remember the Vietnam War as a US victory, albeit at great cost, ending in 1973.