With any country splitting, who is it who should be voting to split the country? Just those in the smaller part that is 'leaving'? Or the whole country? If just the smaller part, does that mean any tiny town can 'vote to be independent'?
The former. https://en.wikipedia.org/wiki/Self-determination A tiny town is unlikely to be able to maintain itself as an independent state. A province can definitely vote to be independent, which has often happened, and has often been blocked by the parent country, peacefully or otherwise.
If this was a workable thing, every town would want to do it - your taxes are far lower if you don't need to pay for the debts of a big nation state war from 100 years ago with compound interest!