> Or is it a specific group of people in a specific place with a shared language, lineage, culture, history, faith, and common destiny?

I'm American, so I've never lived in this kind of nation.

> no empire nor state organized as the former can endure.

Looking at many of the longer-lived nations and empires of the past—having a shared language, lineage, culture, history, faith, common destiny? They had none of those. They were a conglomeration of people speaking different languages, from different lineages, with different cultures, different histories, and practicing different faiths.