Earlier quoted context omitted.
The pedestal contemporary people put national identity on is just that, contemporary. National identities didn't arise naturally. Many of them were very thoughtfully and intentionally invented. For most of human history, the idea that people over a geography the size of Engalnd would see themselves as one people would've been ridiculous. It's really only in the last 200-400 years that people have accepted the nation…
Oh really? National identities didn't arise naturally? Ask the Greeks and the Italians
https://en.wikipedia.org/wiki/Social_War_(91%E2%80%9388_BC)
It wasn't until the early 1800s that a group of nationalists and aristocrats started a nationalist movement.
https://en.wikipedia.org/wiki/Italy#Italian_unification
Greek nationalism developed around the same time. Before that, the territory that is modern Greece passed in large pieces between different empires and the Catholic church. Previous to that the Polis or city state was the highest political authority and the unit of place identity. There was some flirtation with larger alliances like those that fought the Peloponnesian War but they were loose and did not last after outside conquest.