It's certainly sustainable, but a three-generation nuclear family will need two or three farmable ("arable") acres to prosper. Expect the population to diminis

It's certainly sustainable, but a three-generation nuclear family will need two or three farmable ("arable") acres to prosper. Expect the population to diminish substantially. What is not sustainable is high technology, which likely can't be quickly restored, once it crashes. It might take a couple of centuries to put all the systems back in place, if the crash is deep enough.