The two KINGDOMS of Scotland and England were united well before the two NATIONS were. Separation of the state of Scotland wouldn't mean the collapse of the United Kingdom. HM the Q would still be Queen of Scotland.
But the question remains:- What would the nation of England, Wales and Northern Ireland call itself? South Britain? The United States of England, Wales and Northern Ireland?
It can't be a united kingdom because England and Scotland are the two united kingdoms. Wales is a principality and Northern Ireland is just strange.
The Union of England and