We are talking about TSMC and their advanced 5 and 7nm process.
Mainland does have chip fabs but nothing really advanced.
5nm and 7nm is REALLY hard to do and VERY expensive.
Global Foundry tried to make it work and abandoned it.
EUV lithography on layers below M5.
The building must be very stable to make it work.
There are only three companies who do advanced semi fabrication.
TSMC (Qualcomm, Apple and I think AMD)
Samsung (IBM and others)
Intel
Lack of earthquakes another reason for fabs built in AZ. Very expensive equipment and expensive wafers in process damaged and thrown out.