The 1990s' surge of nationalism has been felt in Africa as well. Eritrea split peacefully from Ethiopia in 1993, but went to war in 1998 over a border dispute. Italy, Spain and the UK have all been the subject of demands by separatists. Scottish and Welsh nationalist political parties achieved some of their aims with devolution. Meanwhile, many countries have been getting closer to each other.
Unification is driven by economics.
So we've started to trade-off aspects of sovereignty against economic advantage. Nato is also marking the entrance of Hungary, Poland and the Czech Republic to its ranks. Ironically, although the break-up of the USSR and the fall of the Berlin Wall were catalysts for separatism across large swathes of Europe, they also led to the reunification of Germany. The World Trade Organisation was founded in 1995 to improve trade relations, providing economic prosperity, and thereby leading to reinforcing world peace. Most major nations are members.