It would seem that a couple of millenia would be time enough.....
They haven't had a couple of millenia of contact with Greco-Roman Western Civilization and Christianity like the Scots, for example, have. A lot of European ethnic groups didn't join Western civilization until fairly late in the game and some still haven't gotten their act together and still act tribally (e.g., the Balkans). Believing that all of Europe embraced Western Civilization quickly and painlessly is as wrong as believing that all black people are culturally identical in Africa.