Was the book Imagined Communities? That is an excellent book, but what you need to keep in mind is that, as a historian, theory is not intended to stand in as a narrative for us to fit facts into, but as a tool which allows us to find the language to understand events and ask questions. But it is still an ahistorical narrative, and we have to be careful not to treat it as fact.
That said, I think it provides a helpful way to look at aspects of modern history. Now I’m gonna be real for a minute and tell you that my response is about to get hella Euro-centric.
In the Early Modern period through the beginning of the twentieth century, we saw the rise of the diverse, multinational empire. Those empires broke apart over the course of the twentieth century, and splintered into the nation-state; a political entity held together not by imperial bureaucracy, but by the idea of a shared historical identity and experiences. For that nation-state to sustain itself, there must be an other–a group which does not share that identity and those experiences–for the nation-state to define itself against. We also saw in the twentieth century, in the form of the Yugoslav Wars, the logical endpoint of the ethnic nation-state: genocide and ethnic cleansing.
Now, in the twenty-first century, the idea of the ethnically homogeneous nation-state is tearing apart at the seams as the globalized environment fractures. Nation-states are confronting ethnic, national, and racial diversity, forcing them to wrestle with how to accommodate the “other.” This is why you hear people (like me, alas) referring to the contemporary global environment as “post-modern.” It is also why so many “Western” nations are having a collective violent temper tantrum.
As you can see from what I just wrote, the discourse on the nation and identity etc provides a helpful lens by which to view the last 500 or so years of history. But the fact that it’s helpful doesn’t make it true. Every issue I addressed above is 1000x more complex than my two paragraphs will ever be able to convey, and that’s why the theory is a helpful way of processing large periods of history. But as your analysis becomes deeper and more nuanced, this theoretical framework may (and probably should) feel more and more remote and overly simple to your analysis.
As for the last part of your question: “Should there be a shared history for shared values?“
That, to me, implies, that I can just imagine a past. Ethno-national groups do imagine their pasts, absolutely (if you get me drunk enough, you are likely to hear me yelling about how I’m mad at Ancient Rome for fucking with my people ~2000 years ago), but those pasts are nothing more than a collection of narratives strung together to serve some sort of ideological purpose. The reality of history is that one million narratives and chains of interaction are ongoing at any moment in time, and that historians can only incrementally understand them through careful questioning and analysis.
And as for “shared values,” aren’t those just as false as an imagined past?
I hope this answer was helpful; don’t hesitate to ask follow-up questions if you have any.
Some titles you might enjoy in relation to this line of questioning include:
The Landscape of History: How Historians Map the Past by John Lewis Gaddis
Writing History in the Global Era by Lynn Hunt
Can the Subaltern Speak?: Reflections on the History of an Idea by Rosalind Morris
Gender and the Politics of History by Joan Scott
Silencing the Past: Power and the Production of History by Michel-Rolph Trouillot