China is at or near its 21st century peak (getting old before it gets rich), and the US has a massive number of strong friends and allies, including a European Union increasingly wary of China.

It's a different Cold War from the USSR, but democracy may still again prevail against a totalitarianism.

Chinese GDP growth has slowed dramatically, and it’s GDP per capita is still at the level of Mexico. It’s population is projected to decline dramatically, and it has a very unfavorable age distribution.

It probably won’t get more than some small multiple larger than the US economy and it may never approach the US in GDP per capita.

My point is that the the imbalance is unlikely to get large enough that they US keep fielding a credible nuclear threat.

So again what has changed that makes conventional war between nuclear powers likely or possible.