Just can't let go

My simple answer is that there never are reasonable compromises when it comes to nationalism and religion. Natural resources, ports, religion can't be comprised away, in general. Israel is one example.

At the grand level, nationalistic groups have been breaking away from larger states - see Yugoslavia for a violent example, and the Soviet Union for less dramatic examples. I think it's "cycle of history" stuff - groups get together under dictators, or to protect themselves from foreigners, and then live together for a while until the fight to separate.

Looking at recent history, Soviet communism and Chinese communism see to be at the center of the latest cycle.