TSMC has fabs in the PRC as well. And they are building one in Arizona.
TSMC only manufacturers it’s most advanced chips in Taiwan, they keep that technology out of mainland China. The new plant they built in north Phoenix is going to be manufacturing the most advanced ones also. Supposedly it’s almost a copy of the plant in Taiwan. Putting it in Phoenix is to keep the ability to manufacture cutting chips out of the reaches of the Chinese if they should invade Taiwan.