Sorry but you know that Nokia, Sony Ericsson & HTC essentially ceased to exist on the smartphone market, right? Let alone the high-end one.I haven't heard such a confirmed or non confirmed plan to ban Xiaomi/OPPO/Vivo/etc.
If that happen, Samsung, Apple, Nokia, Sonny Ericson, HTC will be the ones that can supply high end smartphone with 3nm to China market and will reap benefit from such a situation. But I dont think US will ban the rest of Chinese smartphone makers because they realize 3nm still need huge market.