https://wccftech.com/the-tsmc-arizona-plant-is-a-12-billion-capitulation/

Taiwan Semiconductor Manufacturing Company TPE:2330 is reportedly setting up a 5nm fab in Arizona, according to recent reports. Should the reports be true, it would be an about-face from the company's prior stance where it resisted the idea on the basis of cost and necessity. 

In TSMC's view, the need to have such a facility in the US for defence projects and other sensitive customers is a moot point. TSMC's own internal security mechanisms are enough to thwart industrial espionage attempts from China (after all, China is home to other chip fabrication companies that TSMC would count as a rival). It would be painstakingly difficult to plant in a hardware backdoor into chips at the hardware level, as they would come up in the validation process (when the physical circuits are compared against the designs sent by the client) at TSMC or upon delivery to the client.