I take the point about the further divisions and local loyalties, dividing that sense of Englishness. Having lived in Scotland, I saw the very same thing there, if not stronger.

The thing that unites them there is the common enemy, in this case England. It is that that creates the concept of Scotland as a united nation and of Scottishness.

It has happened in England too. Notably during the early days of World War Two. The local loyalties take a back seat in the face of a common foe. Not that you would notice from the banter, especially in the forces. Ribbing and name calling, like Taffy, Jock and suchlike. Difficult to tell who the foe was sometimes.