They had the same roots, language, religion, etc.
I don't know what you were thinking when you wrote the above. I don't think I should need to point out that the English and Americans also have the same language and religion.
I'm not sure what you mean by the same 'roots', but if you're talking about race then all I'll say is that the Greeks tended to resemble the different races in their various hinterlands rather than share any pan-Hellenic racial features. If you're talking about cultural roots, then that's not any more true of the different Greek-speaking states than it is of the English-speaking states. Greeks founded Greek states just as English-speaking people founded America. OK, America THEN became influenced by other cultures (German, Spanish, Irish, Scottish, French, etc). But did that not also happen to the Greek states? The Greeks of Alexandria came to worship Egyptian gods as much as their own, the Greeks of Asia Minor came to worship Asiatic gods like Cybele, the Greek states of Italy become Italicised, etc. Another point worth considering is that England itself has arguably changed as much from the time that the English founded the 13 colonies as America has. Possibly not, but if so, would we have to make modern England a separate civ from Elizabethan England because England has since undergone Caribbean, Indian and other influences?
Linguistically, the English and Americans have far more in common than Greek linguistic groups like the Dorians and Ionians. Perhaps this is to be expected given the comparative ease of transport between now and then, but this still has to be taken into account when using language to separate the English and the Americans (a suicidal strategy methinks :suicide: )
You mention the Olympic games a0s a factor uniting the Greeks: YES YES YES. I'm not arguing that the Greeks were not one civ!
The 4 Pan-Hellenic sanctuaries are other uniting factors.
But there are modern Olympics. I know they do not exclude non-Anglophones (they're French in origin), but the point is that they bring both together. There is also the Commonwealth games that to some extent do exclude non-Anglophones by the fact that participation is restricted to members of the Commonwealth. America is not a member of the Commonwealth because it was not part of the British Empire that fell after the 2nd World War,
but the other English states are. The Greeks had artificial institutions like these because it was a way that Greeks could come together in a world in which they were surrounded and constantly threatened by barbarian. America is so dominant and strong that it needs no way of expressing its brotherhood with other English speaking states. In saying that though, virtually all English-speaking states have been as thick as thieves since the Great War, and non-English speaking nations (e.g. the French) notice it.