This classic work in the history of nationalism argues, put most simply, that the rise of widely available print (esp. newspapers) made it possible for geographically dispersed groups of people to imagine themselves as a roughly coherent entity called "a nation." 
It strikes me that the rise of digital and social media over the past two decades has brought us close to the end of that 200 year or so history of print and nationalism. Digital media eats away at imagined communities from two opposite poles...
On one hand, digital media is global, it easily crosses national borders. Whereas print was limited by transportation technology, TV and radio by the length of a wave, now teenagers in Macedonia can shape the political worlds of midwestern boomers through Facebook.
On the other hand, the data collecting power of digital media means that broadcasting has been replaced by narrowcasting. We share fewer and fewer cultural touchpoints with each other as we are carved into smaller and smaller marketing niches that serve us up curated content.
The differences across nations are being collapsed, meanwhile the differences between different sub-groups of citizens are being ever more exacerbated. These seem like mutually exclusive dynamics, but I don't think they are really.
Nations have always been immensely diverse collections of people who don't agree with each other on tons of things. But despite those differences, the nation existed in their minds, an entity in whose existence they believed in part because media enabled them to see it.
As the basic structure of our media--the window through individuals perceive what "reality" is (outside their own limited range of direct perception)--changes and de-centers "the nation," it's hardly surprising to see citizens increasingly incapable of finding common cause.
In the absence of a citizenry capable of finding sufficient solidarity w/ each other to wield their sovereignty in a meaningful way thru politics, the state gets captured by authoritarian kleptocrats who use state power 4 their own ends, in the hollowed out name of "the people."
It strikes me that anyone interested in salvaging a robustly democratic conception of "the nation" should focus intently on building a media system that enables citizens to see themselves as engaged in the same project. Doing that, without it becoming Orwellian, is the trick.
I was first drawn to Twitter in 2014 because it had the feel of a town square--a sped up and less geographically rooted version of the political newspapers of the 1790s that I wrote my first book about. google.com/books/edition/…
From the start though, I also harbored the suspicion that even a technology as powerful as Twitter would fall short of doing the socio-political knitting together necessary to sustain a naion. This was, I believe, the 2nd thing I ever tweeted.
Thoreau voiced the common desire to live a fairly small-scale, localized life, a life that was the size of what one could see with one's own eyes and walk with one's own feet. That world was already gone when Thoreau said this. Maine and Texas would soon go to war w/ each other.
And after that war the nation would be re-knit back together on new, abolitionist terms...terms that were always contested but which feel more fragile now than they've ever been as white nationalism rises and the 14th Amendment's vision of birthright citizenship is questioned.
I'm just a poor country historian, so I don't know what the future holds or what the answer is. All I know is it would be bad to let the discourse of "the nation" become the sole property of the right wing authoritarian kleptocrats who're driving rising nationalism worldwide.
When such people grab hold of the fiscal, judicial, and military apparatus of the state in the name of "the people" but for their proprietorial use, then that's a slippery slope toward authoritarianism that's hard to reverse.
Thanks for coming to my depressing as sh*t Ted talk.
Coda: The kerfuffle over the #1619Project is an apt microcosm of this dynamic. Some ppl put forward a compelling narrative about American history grounded in the evidence & current scholarship. A good chunk of the nation *loses its sh*t* over it, and calls it "anti-American."
The whole point of that project, as I saw it and I think the authors intended it, was to further the project of telling an ever truer and more rigorously inclusive story about the history of the United States. Of course some will disagree. History is always an argument.
But folks didn't so much argue with the #1619Project as much as they just dismissed it, wanted it retracted, wanted it to go away. That level of brittleness is not a good sign for a nation.
History as a discipline emerged contemporaneously with the nation-state as a political formation. Nations needed chroniclers to tell their stories, to help produce subjects who believed and were moved by those stories, and who would fight on behalf of those nations.
A citizenry that can't agree on even the most basic starting points and facts of the nation's history is a citizenry that is easily broken, and more easily dominated by those with great wealth, galvanizing populist rhetoric, and little respect for the democratic process.
