That question shows a total lack of understanding of the military, logistics, political processes, and the history of the United States. The loss of the Vietnam unpleasantness was due to several factors, none of which have anything to do with weaponry.
What we call the Vietnam War was lost because the population of the US tired of sustaining the government of South Vietnam. That government was seen in the US as corrupt and ineffective and the voters of the United States tired of supporting them with the cost of US lives.
You really need to read your history. Generally, the population of the US will support wars where they can see a direct threat to the US. By the time we withdrew from Vietnam, we had been in that country for over 10 years, no real progress had been made politically and our population tired of supporting the South Vietnamese government. President Richard Nixon made the decision that the effort was no longer politically sustainable and withdrew American forces.
It was politics, pure and simple. It had nothing to do with weapons, or tactics, or hardware. US soldiers, sailors, Marines whipped the enemy every time they came out to fight.