I'd like to reiterate the request of a couple others regarding the fate of the islands formerly belonging to Carolina in the ENA. IIRC the ENA managed to seize some of them and hold some of those; otherwise the ability to project power all the way south to Caracas would be pretty dubious! But I honestly forget which islands wound up controlled by whom; perhaps the French still hold some of them too?
I would think that any of them retained, on paper, by Carolina are in fact under even heavier Meridian influence than the Carolinian mainland. Unless the demographics are heavily butterflied they'd have a much greater proportion of African ethnicity and perhaps the Meridians indulge their distaste for slavery there, formally splitting them off from Carolina and setting them up as nominally independent republics? But that would obviously inflame the Carolinians, including of course the white Anglo-Latino minority who live there. Can the Meridians be high-handed enough to do that?
I hope so but the narrative seems to be setting up rather for the southern American great republic to adopt a Burdenist sort of racism instead.

Which would fit with the impression some of us had that part of the horror of Societism is an adoption of racial stratification. That would trouble me much, since even up to this point the Meridians seem like the most worthy of the Great Powers, and I've long felt that if the Societists are in fact not racist they probably would be far less awful than our Diversitarian sources allege. Certainly if Siam is going to become another Societist regional bastion one would doubt a racist narrative would play well there--it could of course be just a special hell reserved for Africans only, with Asians and Native American peoples and islanders generally regarded on a par with Europeans. But special racism against Africans only seems to go very much against the grain of both Sanchez and the Meridian historical arc generally.
It could also be that there is no explicit endorsement of race as a framework for social stratification; it seems that unlike OTL Marxist socialist traditions that denounce both racism and social stratification the Societists may also despise the former--but clearly support the latter, on what would seem to be an individual meritocratic basis. Since the ability of individuals to demonstrate their "merit" is heavily dependent on both individual family/associate connections and wealth, it could well be that just as the modern USA denies that race is a valid category for discrimination yet in fact remains visibly racially stratified, so too the Societist combine denies that race is a relevant factor yet people of African descent remain disproportionately on the bottom of the socio-economic ladder and politically as well, with any movements to close the gap being suppressed on the grounds of running against meritocracy (with a token handful of successful African-descended individuals cites as proof there is no discrimination) and being some sort of Diversitarian Trojan Horse.
It does seem to me the author has largely wound up casting the UPSA as the actual counterpart to the USA ITTL, so if it winds up as the center of a legally borderless realm of capitalist free enterprise, an oligarchy where all are legally equal but some far more equal than others due to the merit manifested by their superior material fortunes, that would seem to fit. And I take the images of a field of uniform people-icons sucked into what appears to be a collapsar that illustrate the opening of this entire volume as a commentary on both Societism and the OTL US global hegemony.
Especially if the Societists turn out to be more explicitly Burdenist than I hope they do.
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I wonder about other islands and other borders too.
Hawaii--last I looked those islands appeared to be falling under Russian influence. Has this gone forward; is the native kingdom there explicitly under a Russian protectorate of some kind?
With the ENA reaching out to claim Cygnia way over across the Pacific as integral territory, the lines of communication across that ocean become critical; Hawaii seems likely to become a zone of contention if it is not firmly under someone's control or remarkably strong in its own right; the latter, cool as it would be, seems pretty far-fetched.
Novy Muscovy is also a zone where Russia and the ENA could again come to blows and the fate of Hawaii seems likely to be wound up in that. Besides the direct confrontation along the latitude line border and across the sound, there is the question of who moves in to claim the unclaimed Indian territory east of the coastal range ridgeline and west of current formal ENA claims; the map shows this territory is in the watershed flowing east so the Russians would be pretty bold and obviously aggressive to move into it; might they however seek to ally themselves with the remnant Native peoples living there to secure the latter from ENA annexation, extending the Russian sphere of influence east while retaining a buffer zone?
OTL the Russian fur traders cultivated relations with select native peoples more or less along the French model in Canada; it didn't mean relations were idyllic but I'd certainly think the Indians of TTL, being so hard done by the Supremicist land grabs of recent decades, would, well, um, Look to the West at this point for help.
Finally, in view of the questions about the Caribbean islands, the status of Hawaii and the ENA in the Pacific generally, as well as their recent debacle on the high seas in the Atlantic at the hands of the Meridians, I'd think that the subject of naval reform and expansion would be a hot one in the ENA. Obviously not so much during the recent pacifist/Patriot interlude, not officially, but any procrastination in building up the ENA navy of the past few years would be one of the political hot potatoes that lead to their being swept out; the new regime has clearly got a mandate to build up the Navy to be second to none and in particular to whip the Meridians at sea, with its hands tied behind its back against other foes, such as a possible Meridian/Russian alliance.
With the Meridians so strong especially in South America, there is little to no connection between the Atlantic and Pacific bases; Drakesland and Cygnia in effect need their own navies, and a heavy investment by the Empire as a whole in subsidizing the necessary infrastructure for them to hold their own while the Atlantic fleet is preoccupied with the USPA (and possibly Russian or other allies swooping down from Europe at the same time). The territory the Russians hold on the Pacific is not so wonderful from an overall resources view (food in particular is hard to come by in those latitudes, though Novy Muscovy is probably good on a small scale, and Yapon can sort of feed itself, barely) but it is good for many crucial naval stores--now of course we are moving fast out of the age of sail and it will be necessary for the Russians to find coal and petroleum on the shores they hold or not too far inland. We know they have the latter but they don't yet! I also think the northern Pacific rim is pretty short on iron, so essential supplies will have to come in from imports or overland, over Russian Asia. Good thing for them their empire has pioneered railroads, but how developed are trans-Siberian communications by now? Is the Russian north Pacific from Yapon to Novy Muscovy, like Drakesland and Cygnia, still essentially a world of its own that must sink or swim with little help from the imperial heartland?
If that will change for maritime Siberia and hence the whole arc with the connection of Pacific to central Russia by rail, it will change for Drakesland too. Still both will remain semi-isolated; Siberia and the Russian Pacific by the sheer cross-country distance as well as challenging climate of any transSiberian route; Drakesland by the rugged terrain the railroad would have to cross. OTL the first transcontinental link in the USA ran through what is here Californian territory; northern tiers came considerably later, only after a southern route or two matched the central one. Here we can only anticipate either of those as the outcome of cooperation with California, but the Californians, despite the origin of many of them from the ENA, will be steering a careful course between the Empire, the Russians, and the Empire of Mexico, with the Meridians as like as not sticking their oar in too from down the Pacific coast.
Where, from their south American bases on the Pacific, they will pose an ongoing threat to ENA ambitions that might well eclipse the Russian rivalry--in fact perhaps the key to the upcoming generation in the Pacific will be a more or less forced alliance between the Russians and ENA Yankees to try to parry Meridian aggression against both?
Or will Russia see the UPSA as the natural ally against ENA in the Pacific, coming to understandings partitioning the gret ocean between them north and south?
And what of California and the Spanish realms between them?