Or, just don't bring a phone if you're particularly vulnerable. What are they going to do? Deny you entry because you don't carry a phone? If we're really at that point, where merely not having some item is suspicious, we're in deep shit.
It's standard for many multinationals and universities to provide blank secondary devices for travel to China that are synchronized with data after getting past the border. They are then erased after one gets back, because Chinese intelligence has broken into hotel rooms and installed keyloggers before.
Adding the USA to the list of countries where this is done would increase costs but it wouldn't be some nightmarish unprecedented problem.
if you don't know yet, we are in deep
I wouldn't want to be the one to test this. That's an indication of how deep we dug ourselves in.