I agree the Vietnam War could have ended in a "victory", if the United States had used all its military power early in the conflict.
Two factors worked against that: the demand that the US keep large conventional forces committed to NATO and poor leadership, both civilian and military.
Tragedy flowed from both factors.
I was a radar navigator on B-52s during the late 60's-early 70's. We could have won the war in two week or so. By bombing the dike systems on the Red River during monsoon season, North Vietnam would have been under water. Game over!