Just one minor nit-to-pick. As a Vietnam veteran from the post-Tet offensive period, I believe that we DID defeat the Viet Cong, but lost to the North Vietnamese regular army with the full backing of China. Here is what really happened in 1968. https://history.state.gov/milestones/1961-1968/tet#
Not the shift with political positions and public opinion. It is claimed that Johnson said, "We have lost Walter Cronkite. We have lost the war."