Yes, Rome brought advances along with their thuggery. It is a mixed bag. I am neither praising them nor condeming them.
Northern and Eastern Europe are not to blame for a lack of European unity. It has something to do with numerous different cultures, languages, and a number of differing worldviews. Besides, who says that Europe has to be unified? Must North America also be unified?
And I may have used the wrong word when I said unite. I really meant the civilization brought to the world by the Romans and the Greeks before them may have been better for the people of the region had it spread over all the land mass of Europe. We may have had less of the different world view and culture and languages you speak about. Ergo less conflict and wars.
Just as I think most of South American is better off having one cultural heritage from Spain. Other wise it might still be as barbaric as Africa which didn't have one conqueror.