One of these days I really need to do a serious research post on how experience in Eastern Europe, particularly during the early Medieval period, differed from that in Western Europe. Basically, Eastern Europe was subject to a series of invasions which simultaneously layed the foundation for later developments and isolated it from Western Europe. Goths, Huns, Slavs, Magyars, Tatars (Mongols), and Turks in turn harried the area east of the Elbe in the north and the Alps in the south.
I suspect that this series of invasions resulted in both the fragmentation (Balkanization) and nationalism that we see today.
For a combination of reasons including the poverty of the historical record and the predisposition of Western Europeans only to be interested in the history of the Franks, Germans, and Anglo-Saxons there’s an enormous gap in the history taught in our schools.
The Franks, Germans, and Anglo-Saxons have all seen themselves at one time or another as the successors of the Romans. It might surprise you to know that the Russians do, too.