Vietnam has already cost the United States countless millions in treasure and the lives of fifty thousand kids; let China have it!
Having said that, it is much more difficult to join forces with a nation which a) we did NOT vanquish and that overran our ally and had our own embarrassing, disgraceful running away -- thanks D.C. politicians, Democrat Congress with funding halted to RSV -- with our tails between our legs; and b) maintained the political system that was the cause of the war, namely COMMUNISM.
Also Vietnam is not as far out time was as the Pacific Theater of WWII, but I imagine anything is possible in due time, you just might see joint Socialist Republic of Vietnam and USA military action against the Chinese in the South China Sea. More weird things have happened in world history. I dont decide it or determine it, I just call it as I see it and in the future, like it or not, I see Commie Vietnam and USA cooperation. (Would be nice if they totally dropped Communism like the Poles or Hungarians in the meantime, though). They in fact do know the benefits of capitalism, even if in their Vietnamese pride they still insist on calling it Communism.
And another thing. As a prerequesite for ANY COOPERATION I would sue to high heaven a final account of every last American MIA, down to every single last bone or any assortment of stored bones in boxes in Vietnamese warehouses in Hanoi that the SRV damn well knows where they are. But the truth is, the Vietnam "Conflict" is in fact now over and in some aspects we are just going to have to man up, suck it in, and "let it go"--maybe not as individuals who went through that holy jungle hell, but the Nation as a whole. Especially when faced with Beijing, those BASTARDS. I don't dishonor the service of any man that served. The Confederacy eventually joined the union and we went forward as a nation. Things are tough. Things hurt. Things are not easy sometime. Unholy alliances result. The enemy of my enemy is my friend. Ad infinitum.