Yes. But some large countries are homogenous enough to be fine. The US, for all its flaws and divisions, is arguably homogenous enough to stay together (though

Yes. But some large countries are homogenous enough to be fine. The US, for all its flaws and divisions, is arguably homogenous enough to stay together (though I guess we'll see what the next 50 years bring). China and India (modulo their regional minorities) are homogenous enough to stay together. Another option is to have multiple levels of government where many important decisions are local but others are made at a higher level. The EU is a great example of this (modulo Brexit).