With all the mention of war, people of the USA seem to forget that it's not a given all of USA would "stand" for the same side — it is so big and so polarised (with the latest political climate), that I wouldn't be so certain of it.

If we even imagine a war between nuclear powers like Russia and China vs US, I would hope that most of the smart, liberal population of USA would realise that this is not about "winning", but rather about having fewer casualties (iow, fewer dead people). And that is best done by less war (ideally none), and if war is in progress, figuring out a way to stop it as soon as possible, even if it means making some concessions.

While war does lead to engagement of industries which might have been long forgotten, in the big scheme of things, it is always an economic loss for anyone directly being hit. US does have the benefit of not having been directly hit for centuries (if we exclude a terrorist-style attacks like Sep 11th, or single instances like Pearl Harbour), but that would be hard to avoid in a conflict between Russia/China and USA.

And that's when polarisation in a society comes out, and with such a long, lingering list of "unresolved" issues, I wouldn't allow myself to predict an outcome.

While I am not a fan of Chinese or Russian leadership, I definitely hope that there are enough smart people in there to not allow such craziness to unfold either.