China can't have a direct war against the US, either. So, like with Russia it's a calibrated game and proxy conflicts (which is what Taiwan would be)
Even if the machinery is effectively destroyed, the talent pool could be enough to accelerate rebuilding the technology in China, so that scenario is I think damaging to the US/the west to a degree that exceeds the Ukraine conflict many folds.
Look at how HK was destroyed.
What will probably happen is that the smartest and skillets one will flee, most probably to US and Europe, to our advantage. There will be a carnage of repression with abusing jailing and deportation for the one staying to resist to défend freedom.
And China will import mass of Chinese immigrants to replace the majority of the population of the island in a few years. Then it will become just another shitty Chinese island with a weak economy and little activity. But the technology parks will certainly not continue to run like if it was nothing.
In the same way that HK is mostly deserted nowadays.
The US can fab 2nm if they buy the machines from ASML.
According to Taiwan, its local TSMC factories is poison-pilled. If China invades, all of ASML's tech gets remote-disabled. Since the US economy strongly depends on these chips, they have no choice but to stand by Taiwan. If, on the other hand, the US has the capability to make these chips on their own, that fundamentally changes the situation.