1) operating a large plant in US is much more expensive than in Taiwan and it will bring less profit. So it it not financially motivated decision.

2) US can restrict export of chips to other countries and TSMC will lose money in this case

3) US can copy the secrets, share them with Intel and AMD, and make chips without paying TSMC

So this looks like a risky and not profitable decision to me.

Ensuring availability of goods?

David Ricardo never said that England should depend on Portugal for wine, and Portugal on England for clothes.

Edit: apologies, I read the original point as referred to the USA as a decisor, not to Taiwan (as the poster intended). The former point remains, about the clear opportunity for strengthening ties.