Vietnam was never winnable.
The US should never have been involved in another country's civil war.
American politicians are responsible for the death of over 40,000 American servicemen and God knows how many wounded.
I guess you don't realize that the North Vietnamese were heavily backed by the Soviet Union with weapons and advisers and financial aid? We intervened in Vietnam to keep the whole country from falling into the Soviet orbit and to keep tens of millions of people from having to suffer under Communist tyranny.
And if liberal Democrats had not insisted on insane rules of engagement for our troops in Vietnam, our casualties would have been far fewer and, at the very least, South Vietnam would be another South Korea today.