They were still originally defined based on geographical location and a shared lineage within a region. The fact that the culture was split and dispersed at some point in history doesn't take away from that.

My point is that culture and nationality aren't things that are any more worth being proud of than race is. An individual is no more responsible for the culture they're raised in than they are responsible for the colour of their skin.

Being born in a particular culture or nation doesn't automatically make you a better person, any more than being born a particular race makes you a better person.