> This is pretty bad for Taiwan geopolitically though... once US chipmakers have a plausible local manufacturing alternative, the US is less likely to risk WW3 by standing up to China if/when it tries to annex Taiwan.

I doubt it changes much to the demise of modern world. The industry will still go down given that you have many, many, many more things in the semiconductor supply chain that is run by some single vendor in the world from Taiwan, and that includes consumables too.

US may get a modern fab, or two, but it will still eventually run out of many know-how intensive inputs for those fabs.