After WWII, it seemed that the trend was toward consolidation. Nowadays, however, it appears just the opposite. A few examples leap to mind: For starters, there was the Brexit vote just a little over a year ago: The British people voted to soon leave the EU. For awhile, the Kurds have been wanting their own state (Kurdistan). Although Iraq (from which it would secede) and Turkey both oppose this, it would not be surprising to me if it were to come about. Scotland is now talking about leaving the UK, and becoming a fully sovereign county again--no more an actual part of Great Britain than, say, the United States is. In northern Spain, the people recently voted--overwhelmingly--to secede, and form their own nation of Catalonia. (This would, of course, include one of Spain's larger cities: Barcelona.) Even in the US, California is making noises about leaving the US, and forming its own nation. (Certainly, this would not provoke a civil war, as occurred in the 1860s. In fact, many of us would be happy to see California go; the Democrats would never again win another presidential election, absent California's 55 electoral votes.) What do others think?
All things being equal, it would probably be a more peaceable world if every nationality had their own nation. Unfortunately to get there usually requires a Yugoslavia-like war.