Europe.....Britain left.
Russia broke up.
Yugoslavia broke up. Czechoslovakia broke up. The Catalans want Independence.
The Scots want Independence.
The Chechens want Independence.
The Basques want Independence.
God knows what the Irish want.
These are countries with populations less than most Indian states. They still cant stay together and we Indians have been living in comparative harmony for almost 70 years despite differences in religion, culture, language and food habits.