What causes Scotland to be a country, but not Brittany?
I could use many examples here from European history, but I think (for several reasons) the most pertinent example would be Brittany. Historically, it was a completely independent country, and it also has the same "Celtic culture" that places like Scotland hold up as a major reason why they should be considered a country in their own right.
Yet Brittany is clearly considered nothing more than a region of France. People would probably think you a little odd if you referred to Brittany as a country.
What is the political reason behind the fact that Brittany was subsumed into France and lost country status, but Scotland (not to mention Wales and Ireland, before the Irish free state) were subsumed into the UK while retaining country status?