What 3 nations saw the vietnam war fighting?

Why did the U. S Enter the fight?

Was the U. S successful?

Vietnam, Cambodia and laos

The U. S. entered the Conflict in Vietnam to stop the spread of Communism.

Considering that the North Vietnamese defeated and took control of South Vietnam, Thus uniting Vietnam under a Communist banner. I'd say the U. S. failed to halt the spread of Communism in Vietnam, therefore failed