Crediting Colin Woodard's American Nations for the map, Yankeedom and Midland(s) would have been nice. The five counties in Oregon that petitioned to secede and join Idaho included those in coastal SW Oregon. The Texas panhandle should be in Heartland's Texahoma state. East Texas and part of its coast belong in Southland. West and parts of south Texas belong in Astlan. Austin should be a free city state like interwar Danzig (Gdansk). With the ranchers of eastern Oregon and the citizens of Denver and Boulder in the same country, civil war will go regional.

Definition of a nationality: a people united by a common myth as to its origins and a common hatred of its neighbors.

Nobody in Spain would agree with your classifying so many regions as "nations". The Pais Vasco and Catalunya certainly. I lived in Barcelona for 2 1/2 years and speak Catalan, so I expect we can agree there. Pais Valencia and the Gallegos are quite weak in the nationalism department, as you'd see if you went there.

I'd be very happy to secede the Southland and let them do their huntin', fishin' and churchin' so the rest of us could become a civilized country like Canada. https://medium.com/illumination-curated/secession-2-0-the-big-sort-continues-d45527935a78

The other secessions you depict would produce violent border disputes in a country where the % of people who are armed is the highest in the world. Don't expect amicable divorce.

The Quebecois don't secede from Canada for the same reason the Scots didn't from the UK: fear of immediate bankruptcy and cutbacks to the welfare state they could never afford on their own.

Contrary to your view, the minimum efficient scale for sovereignty has been rising relentlessly. That's why the pooled sovereignty of the EU works. Returning to the "tiny-ist" sovereignty model of medieval Italy would be a nightmare. The Palio in Siena and the towers of San Gimignano do not have peaceful origins.