We lost politically because we still have traitors like Kerry, fonda, code pink, demorats and other turncoats.
The US continued the war, and continued to support it, through Nixon.
Nixon won re-election is a landslide, with the men largely home and the draft ended, and South Vietnam still free and sovereign and in control of its territory. US air power was still needed to protect them from Russian-backed aggression from the north, but as the easter offensive showed, with that support ARVN was quite sufficient.
The war wasn't lost at Tet. It was lost in the Watergate building.