Now you are side-stepping from the main line of our debate. I am looking at the present reality, not what could or might have happened. What happened is what we have today, right? So, the present fact is China is a nuclear power with second strike capacity. This makes China rather untouchable.
Now, if, as you suggest, China, as one of the few Communist nations (in Chinese characteristics) in the world, goes down in ashes, what would fall on Vietnam as another one of the few Commie nations?
Do you think changing governance ideology is as easy as changing your shoes?
Now think if the VCP, which means the state of Vietnam with, at least, a large portion of the people are in support of, had the power to choose letting China go down or letting, say, Japan, go down, which one would it choose?
If I were the VCP top person, I would choose Japan to go down. Because, China's going down would mean I would be also going down in flames in a couple of years.
When China needs some strategic move with credible excuse, the US always comes in handy.
They learned propaganda from the Nazis, but they also learned bad strategy-making from them alongside.