Re: What happens when...
I'm extremely anti-CCP and angry with many things that the PRC has done to Taiwan and others in recent years, but still I agree that cutting them off from western technology is a bad idea.
Having said that, Taiwan and South Korea have highly unique environments that are difficult to replicate just by throwing money and resources at the problem.
China has been investing tens of billions, poaching top talent from Taiwan fabs and blatantly stealing American/Taiwanese technology but they are still a long long way behind the most advanced Taiwanese fabs. They have only just figured out volume production on 14nm chips and much of the critical technology involved was imported, not home grown.
I don't see China making any seriously rapid advancements on home grown tech under the current political regime.