The issue is there isn't enough of those small environmental economies to support everyone that exists today without the technology, logistics and trades that are in place today.

You can farm and fish the entire undeveloped areas of NYC, but it won't be enough to feed or support the humans that live there.

You can say that for any metro area. Density will have to reduce immediately if there is economic collapse, and historically, when disaster strikes, that doesn't tend to happen immediately.

Also humans (especially large groups of them) need more than food: shelter, clothes, medicine, entertainment, education, religion, justice, law, etc.

> The issue is there isn't enough of those small environmental economies to support everyone that exists today without the technology, logistics and trades that are in place today.

I agree. I expect some parts of the world will see some black days. Lots of infrastructure will be gone or unsuited to people. On top of that, the cultural damage could become very debilitating, with people not knowing how to do X, Y and Z without the AIs. At least for a time. Casualties may mount.

> Also humans (especially large groups of them) need more than food: shelter, clothes, medicine, entertainment, education, religion, justice, law, etc.

This is true, but parts of the world survive today with very little of any of that. And for some of those things that you mention: shelter, education, religion, justice, and even some form of law enforcement, all that is needed is humans willing to work together.