We passed off a winnable conflict to South Vietnam's Military and Political system, and they would have eventually defeated the Commies IF the United States Congress would have continued to supply ammunition and fuel.
The one thing South Vietnam didn't have was money, they were broke and couldn't buy resupply.
The cowardly traitors that lost the Vietnam War were the US Politicians, American Media and the dope smoking Baby Boomer Hippies that run the Democrat Swamp now.
And the US Congress cut off the money to the RVN.