If US law mandates Apple and Google provide a way to unlock phones on demand, how exactly do people in other countries enjoy "proper encryption"?
Manufacturers in other countries can use a forked Android.
Also, of course, it's entirely possible to use encryption on a smartphone which is not tied to the phone's lock state. I have apps now which aren't unlocked with the phone; they have separate credentials. So they'd need to mandate not just phone-unlocking backdoors but also backdoors in that type of app. Keyloggers and such could capture fixed credentials, of course; it's always an arms race. But technology tends to outpace legislation and regulation.