How did regions in the Classical Greek World administer themselves? To what extent can they be considered to act as a single entity, rather than individual poleis?

by Total-Potato

I often see in sources certain regions, particularly islands, but also for regions such as Boeotia, that the 'Boeotians' or the 'Lesbians' did something - as if they had one policy and were under a single administrative system.

For example - from Thucydides 1.115.3 and the Samian Revolt in 440BCE.

Accordingly the Athenians sailed to Samos with forty ships and set up a democracy, and took hostages from the Samians ...

However, this seems contradictory to how the politics of the Greek world seems to be explained elsewhere - the idea of a polis and its people dictating its own policy. Rather than a more modern idea of a state, the citizens' allegiance lay with their polis.

I'm asking specifically about the 5th Century BCE, perhaps including examples of Attica, Boeotia and Samos.

So how united were the the cities of these islands and regions and to what extent can they be considered to act as a single entity?