Sometimes the Greek city states existed as independent poleis, but often they were dominated by the larger ones (mostly Athens and Sparta), which brought them together in various alliances where the larger city state would imposes taxes, military duties, and social and political expectations on the smaller city states. The clearest example of this would be the Delian League, sometimes called the "Athenian Empire." This goes to show how throughout history, macro political organization has always trumped micro political organization.
As for your idea of each Somali tuulo having its own currency, administrative structure, laws and basically state----I have to say it's very unrealistic and sounds like a retarded idea that does not account for resource scarcity, low human capital, etc etc....
