What would happen if say, Foxconn no longer assembled phones? How would Apple, for example, recover their supply in any reasonable time? You can't just spin up that capability overnight.

Seemed to me that if China wanted to amp this up and play hardball, they could just give Tim Cook a phone call and tell him they won't be making iPhones anymore. Estimates I've seen is that about 40% of Foxconn is Apple products. They could probably replace this demand with more Japanese/Korean/Domestic IHVs, combined with banning domestic sale of iPhones and accelerating the marketshare loss that's been ongoing.