TSMC is both a monopoly for the newest chips and a geopolitical risk in the case of China taking over TSMC in Taiwan.
I think that if TMSC has a subsidary in US, it would be really hard for TSMC Taiwan to block TSMC US from licensing IP from it after the knowledge is transferred. Regarding the monopoly status: sure, healthy competition is good, but it's something competitors (Samsung, Intel) should tackle on the market.
