We fought China in Vietnam by proxy and together with the leftists present on our own turf assisting in the communist cause, the U.S. was unable to finish the job. You have to remember, the Chinese leaders place little value on human life and they have many lives to donate to what would likely be a very protracted engagement. It is for certain, the U.S. would have to have a draft to sustain the effort and the MILITARY leaders would have to be the directors of the war, not the stinking LEFT-WING POLITICIANS.
Not all were proxies.
Yes, in fighting the Vietnamese we were fighting the Chinese by proxy. But we were also fighting the Soviet Union by proxy at the same time. But if memory serves correctly, China invaded Vietnam shortly after the U.S. departed, and got slapped silly and humiliated by the North Vietnamese". They pulled their troops back into China like limping dogs.