No one is preventing you from leaving the USA. Most countries are just making it difficult to enter. I'm all for having more open borders, but that's probably not what you're arguing for.

No one is preventing you from starting your own community either. There just isn't any land remaining that isn't already owned.

And the "punished based on the rules of the given community, or expelled" thing is describing a government, although because of the aforementioned lack of unowned land, they only expel immigrants nowadays.