So as I currently understand it, a lot of historians doubt if fuedalism even truly existed in the way it's often portrayed. And if it did then it probably only followed the general representation of it on the highest level.
Still, there does seem to have been a semi-institutional hierarchy between aristocracy across Europe with kings and dukes and counts. And it also seems like on the top-level, these hierarchies were quite similiar (e.g. the king of Sweden had a similiar relation with his direct vassals as the king of France).
Where did this hierarchy (at top-level) originate, and more importantly how did it spread across Europe? I'm especially interested in regions that seem to have been relatively late adopters like Scandinavia, Ireland and Eastern-Europe.
If I completely missed the ball on this one, please tell me as well.
Here are several threads regarding the concept of 'feudalism' and why the popular understanding of it is misguided. These might give you a better understanding and help answer the question.
For the beginning of the feudal kingdoms, I highly recommend Patrick Geary's The Myth of Nations. If you are interested in reading about real development of feudalism with its complex hierarchies of courtiers and clerks, there is nothing better than R.I. Moore's The First European Revolution
Feudalism was a general phenomenon with many distinctive regional variations and developed at different dates in various parts of Europe. It was, in the former Roman provinces like Gaul, a process of the fragmentation of an imperial order and its transformation to one of personal allegiance and obligation. The rise of commercial cities through a monkey wrench into its uniformity, as did the periods of quasi-imperial control, as with Charlemagne and the Ottonians.
Obviously it's a complicated history, certainly not agreed upon by all. The most eloquent critic of our romantic ideas is Susan Reynolds in her book Fiefs and Vassals: The Medieval Evidence Reinterpreted
Hope this is helpful to answering your question.