Great question.

One of my articles addresses the concept of "national narrative" in a summarized way.

https://medium.com/tiered-democratic-governance/the-national-narrative-68946aaf9007

The narrative(s) may be formal, sanction by the government, like Manifest Destiny. Or it can be informal, like Canadians when they agree that they are "not American." Not all citizens will follow that narrative. But enough will to form a stereotypical concept of what it means to be from that nation.

And there can be competing narratives in the same country.

Medium B. Kean spent 30 years in Russia, setting up various business units. His articles give great insights into the mindset of Russians. They do not think like us. They do not think like Ukrainians. Just from how each side conducts this war, we can see the difference.

National narratives are artificial concepts. They have been created, which means they can also be taken down.