I recall one of the problems with assembling the Mac Pro inside the U.S. was that there simply aren't certain parts available outside of China. In this case, a very specific type of screw had to be imported before assembly could begin. Even if Apple begins to diversity its supply chain, there are some things that can't be easily found outside the People's Republic, due to the scale at which China can produce disparate parts. Also, even though Apple uses a number of proprietary parts, many others are commodities, also used by their competitors. Moving that production out of China would require them to convince Lenovo, Nvidia, Intel, AMD, HP, Asus, etc. to also move production elsewhere. So, this is going to be a chronic problem with the CCP's authoritarian policies and China itself being a choke point in the supply chain. Apple may be able to alleviate some of that, such as production issues with the MacBook Pro in Shanghai due to the quixotic no-COVID policy, but there's only so much that can be done, even if Tim Cook is really good at this.