The war could have been over by 1967..if we had actually attacked NVA with enough resources. NVA was just not as prepared to fight in the early years.
They weren’t getting much supplies from China..the warlords took the supplies that were shipped into southern China and we should have blockages NVA and refused to let the Russian ships in. I remember watching the Russian freighters steam by us in the Gulf of Tonkin. Instead we tried fighting a war of attrition..ignoring the things we were taught about warfare. We should never have allowed NVA to continue to fight the war in the South.
Cold war fears may have had something to do with it. Nobody knew if Russia was nuts enough to really want to nuke a large part of the globe.
Why did we just level everything bigger than an outhouse, pound them senseless with napalm and 16” shells, and then land the Marines on the beach closest to Hanoi?