Most cities, now, have whole tent and RV encampments created by poverty, addiction, and mental illness. As the rich get richer under capitalism the people at the bottom are being pushed out of "mainstream" society all together. And since the mainstream society is not yet willing to euthanize them or able to deport them to some far away foreign land never to be seen again, they have taken to living in alternative communities wherever and however they are able. Usually right in the middle of the cities that no longer have any use for them.
But there are many, many millions more poor people living in shacks and abandoned and falling-down structures all across America. We would be shocked to discover how much of this is going on out there if we were to actually see it for ourselves. But no one in the mainstream of society wants us to see it, or to even acknowledge that it's happening. Much of the United States has already become one of those "third world s***-holes" Trump was disparaging. Nearly every small town in the country now days has 50% of it's population living well under the poverty line; averaging maybe 8 or 9k per household. And most of these towns have lost half their population in the last 30 years.
The number of people in need of some alternative social order is massive. But so far there have only been a few reasonably successful sub-communities set up that I am aware of. I saw a documentary on one in Hawaii that was working well, but didn't control the land it was occupying. And someone was trying to set up a tiny home community in California aimed at homeless vets. But the cost outlay and the oversight required was expensive. So how functional it was ever going to be was questionable. And of course. all the rules of regular mainstream society are designed to thwart exactly this kind of alternative living. So that's a constant problem.