In modern times this isn't really the case. There tend to be immense legal restrictions on movement, let alone living + working in different areas. And the differences that do exist between even nations within the same "sphere" tend to be relatively negligible compared to, again, the sort of monumental differences you'd see just between different Greek city-states like Athens/Sparta.
There were extreme legal restrictions on movement in Ancient Greece, too. You couldn't just pack up your bags and move to Spara or Athens and become part of the citizen class.
And as a non-citizen, there were a lot of different ways that you could be abused by citizens, with little recourse.
Just because despotism and abuse was decentralized, doesn't mean that it wasn't despotism and abuse.
In your belief, from what comes Plato's link between place and state? Places exist before states and often afterward. Can a state exist without place? If a place can exist without any particular state, can a person have a link to a place independent of a state?
Imagine if I'd edited it to read: 'choosing to stay within the bounds of the government, and enjoying the benefits'
Sovereign citizens do enjoy the benefits of the US state, do not reject them nor make strides at moving away from them (from anything I've read).
To paraphrase, Socrates says "Though not explicitly, I have by my actions agreed to be ruled by the laws of Athens by carrying out my life here and not choosing to move away to somewhere with a different set of laws"
[1]http://www.columbia.edu/itc/lithum/wong/textclip.html @ [52b]
I believe Plato will say they consented to be governed by this state, not at birth, but throughout their life by choosing to stay in a place that is governed by this state and enjoying the benefits.