In any case, TSMC is dependent on ASML, which has a monopoly on leading-edge EUV tech.
There is a decent amount of competition at older nodes, like > 40nm. So we'll still be able to make some chips if TSMC completely goes out of business, but obviously it wont scale to the demand and will seriously hamper business, science, and government.
> science
I believe science has access to more compute than it needs. I could be wrong now, but last I checked, a few years ago, the huge computational clusters (both public and private, e.g. @ pharma companies) were under-utilized, especially on legacy-hardware-that-is-still-pretty-damn-good, and scrambling to find ways to engage with outside clients to fill out capacity.
Given what a strategic asset they are, I would expect its not really "conspiracy level stuff" on various plans. After all, the US had attack plans for the UK between the world wars.
Ships would be inspected and food and medicine will be allowed through but all trade goods will be blocked.
But that is all depended on the US and it's allies having a stomach for a naval confrontation or that the Chinese mainland umbrella of long range missiles and air defense can be an effective deterrent against that.