Speaking about divisions: I thought you where asking for the spiritual stuff... People at Spain wouldn't consider all living at that same country.
There is too much history in between. The Bask country existed a long time before the Spanish one (and now they should be considered Spanish?).
Might be better, consider the language that people speaks, don't you think?
That non-so-political division would fit better in all the cases. And might be that Argentininian Spanish wouldn't differ too much from the original Spanish.