That's exactly my point. I did, explicitly, say it was unpleasant, and something you should only do in extremis -- when you genuinely believe that extinction a likely alternative.

But the US could absolutely glass every semiconductor fab (and datacenter, and research facility) in mainland China using a combination of conventional + atomic kinetic options.

I guess we agree then. That would lead to the end of the human race

No, that's almost certainly incorrect. Here's a decent summary of current research: https://www.lesswrong.com/posts/sT6NxFxso6Z9xjS7o/nuclear-wa...

It would be an unthinkable catastrophe, but almost certainly not the end of the human race (and likely not even modern civilization).