I think what might be unique is that the idea of China with pretty much the same borders has persisted for so long. Reinforcing that idea also has been a strong goal for several Chinese leaders over the centuries. Other countries have been divided, expanded, absorbed etc. and seem to have been much less stable in their borders. The idea of Germany for example is very young in comparison and the territory has obviously give through massive changes. It's incredible that China has persisted so insanely long without much change.