This is a fascinating timeline to be sure. Just reading it for the first time today.
Some questions:
Why, after walking out on the Constitutional convention, wouldn't Acadia and Quebec merge into one polity, or at least create a federal alliance? Acadia in particular looked mighty vulnerable, poised between land-hungry Yankees in Maine and possibly vengeful British possessions in Newfoundland. Quebec at least had the sheer population (and despite religious quarrels, the goodwill of the new United States) to deter aggression; presumably if Acadia were known to be at least closely related to if not part of Quebec, they'd be safe.
I don't know my Francophone colonial history well enough to be aware of any cultural or historical reason why the Acadians would not simply see themselves as part of Quebec anyway, nor did I pick up on one in your timeline.
--subscribed, btw!
Oh, well, it seems like breaking up the vaster political units of North America is the theme of this timeline. I don't recall any hints that the Acadians had any reason to regret going it alone--at least nominally. In the absence of any hint of conflict between Quebec and anyone else, I'd think that as two North Atlantic Francophone former colonies side by side, Acadian culture has by "now" (latest update takes us up to 1864 or so) largely assimilated to Quebecois, perhaps with the distinction that Acadians are more maritime oriented while Quebecois are inland (though riverine) farmer types.
Which brings me to ever-deeper and more disturbing questions. To continue to dance around the periphery first--"Rupert's Land?" That sounds vaguely OTL historical to me, presumably this is the political title of what amounts to the domain of the Hudson's Bay Company. Well and good circa 1787, but as Quebecois population continues to grow, aren't they (and later, the independent Louisianiens) going to start intruding on the British claims there, somewhat north of the St Lawrence (pardonez-moi, rive Saint-Laurent!) but most of all in the West, around Les Lacs-Grandes. Sooner or later I foresee conflict with the British Crown over the northwest. Especially between Quebec and Britain--Louisiana has other directions to expand in and a Mississippian culture that probably finds the Great Lakes and lands to the north rather chilly, but the Quebecois have no other place to go and would find OTL Manitoba, Saskatchewan etc their obvious "manifest destiny," whereas unless the British have the foresight to deliberately pre-empt this movement by painstakingly settling farmer colonies via the difficult route though the northern passages to Hudson's Bay, the British interest locally is weak, mainly just to benefit HBC. The strength defending "Rupert Land" from some kind of Francophone expansion, probably Quebecois, would be in the company's claims being backed by the British Empire. Under those circumstances--if Quebec does have a nasty clash with Britain, they might suffer cut-off commerce and naval shelling, yet win on the continent. Or, Britain, foreseeing the outcome, brokers a deal with Quebec allowing some combination of Quebecois settlement of the land and continued HBC profits--either Francophone autonomy largely loyal to Quebec for settlers on nominally British soil of Rupert's Land, or ceding a lot of Rupert's Land to Quebec in return for a continued favored role for the HBC on Quebec's new soil.
Turning south---and east. What happens to the USA? It is true, individual Americans can still emigrate West, to settle in what is now Louisiana. But obviously, the whole identity of the USA is completely changed now. There is no longer the slightest prospect of the vast continental empire many early Americans dreamed up. If anyone has a grand Manifest Destiny now, it is Louisiana. The likelihood of any aspect of US history continuing as OTL is slim to none. Will New England attempt to industrialize as OTL? They don't have much prospect if they don't, but lacking the markets of an expanding West to buy agricultural and mined raw materials from and sell industrial and consumer goods to, can they survive on an industrial basis? Can they hope to trade, again without an expanding Western domestic market to sell overseas goods to and sell the products of to overseas customers? In the Middle Atlantic states--there is room for settler expansion for maybe a generation, and then they are in the same boat as New England. In the slave/plantation South--again, no new lands to establish new plantations in in Mississippi or Alabama, so the possible economic crisis of the plantation economy looms before it gets properly started. And OTL, a major source of capital for developing New England and other northern industry was investments of profits reaped by Southern slave-holders selling cotton from mostly the Old Southwest.
The United States will either fight Louisiana, much earlier than 1864, or it is a completely different society over there, nothing much like OTL Yankees or Dixie.
I know you mentioned the Hartford convention and Yankee secession, but why would that happen ITTL? The occasion for that movement OTL was the War of 1812, and that war was largely about conflicts between Britain in Canada and US settlers moving west. All that is pre-empted here, with Quebec more or less friendly and at any rate decoupled from Britain, and Louisiana first under the Spanish crown and then independent. The only issues left to have a War of 1812 over would be those ones that would draw Yankees into supporting the war rather than opposing it as OTL--impressment of sailors, issues of access to fishing sites, stuff like that. But without the vast backcountry to draw on, ITTL the USA is clearly weaker than OTL and getting into a war with Britain, even a Britain shorn of her base in Canada (but they still have Newfoundland/Labrador, at least until the Quebecois take them from them) is clearly a Bad Idea, impressment or not. So if anything I'd expect the New England States to cling tightly to the Union as their only protection, weak as it is.
So I'm getting the picture--the USA is a sideline in this timeline, and North America is effectively divided between French and Spanish speakers, with Anglophones being peripheral oddities. Even if a lot of Louisianiens and Quebecois wind up being descended from much the same ancestors as OTL US citizens and Canadians, they will speak French.
This brings me finally to the question of where Louisiana will go, which of course is what the whole timeline is all about.
By 1860, the USA had at least one sector--New England--that had caught up to the most industrially developed parts of Europe. And from that base a certain amount of industrialism could be found in any part of the Union whatsoever. Is either thing true of Louisiana? Is there some part of the vast Republic/Empire that has anything like New English levels of industrial development, and how machine-minded are the Louisianiens in general? Even if there is no place comparable to Lowell, Mass, of OTL, are there steam boats and mechanics and boiler factories to be found on the Mississippi as there were OTL? What about railroads?
If Louisiana fails to develop this sort of infrastructure, it might be an opportunity for the US, at least its northern half, to prosper, filling the role of industrial region much as in OTL. It would be awkward though--the Yankees could not rely on access to Louisianien resources or markets as they could OTL, while Louisiana would be vulnerable as well. Perhaps Quebec industrializes more than OTL? That partnership would be almost as bad as Louisiana/USA, but at least both sides speak the same language!
And finally, what about the West? Can Louisiana expand westward to the Pacific? (We also have Tejas loose from Mexico, perhaps it would be more natural for Tejanos to take California?)
I ask all this stuff because you've made me care!
Love the Louisiana flag by the way. It seems to me it would be kind of dark though, dark green bordering dark blue like that. Is there a way to brighten it up a bit, without losing its elegance?
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Edit---
What about California and the Pacific Northwest? OTL, after the Louisiana Purchase, the United States had a clear path to the Pacific Coast, and very quickly took it to establish settlement in Oregon, first via the long sea route to establish fur trading at Astoria. This brought the USA into an additional zone of potential conflict with Britain, which had its own growing fur trade establishment that became British Columbia. It seems that TTL Louisiana does not have the same sense of westward "manifest destiny" nor the seagoing mercantile cultural element of New England (Oregon settlement, even the overland part of it, OTL had a strongly Yankee element to it) and the Latin American politics suggests that sort of inertia too. So what are the chances that Louisiana will even seek an outlet on the Pacific? Will Mexico manage to hold on to California, and even expand north to the Columbia River or beyond? To what degree was British settlement of the Puget Sound area OTL driven by the need to pre-empt the Yankees, and would it therefore be deferred ITTL? What about Russia? OTL, both British and Spanish/Mexican designs on the Pacific Northwest coast were motivated in part by the desire to pre-empt the Russians based in Alaska. And the Russians did venture as far south as Fort Ross, in modern California not far north of San Francisco. Would they have a free hand to gradually work their way south ITTL? Logistics and demographics were against them OTL. The major reason they established Fort Ross was to set up a farming colony to feed their company operatives up north in Alaska. Presumably they passed Puget Sound and the Columbia/Williamette river valleys by because they were already preempted there by British and Americans, but if they could get to Vancouver Island and that region first, perhaps they would be strong enough not to dislodge. This would delay Mexican expansion northward which was partially a race to preempt them from California which they would not need to attempt now. Leaving prospects from San Francisco to the mouth of the Columbia for a later British incursion, an adventurous Yankee claim, later annexation by Russia or Mexico--or a belated Louisianien claim.
And back to the east and the Gulf of Mexico--paralleling the movement of Anglo Yankees into OTL "Old Northwest," ITTL Ohio, we had OTL the expansion into the "Old Southwest", that is Alabama, Mississippi, as well as Tennessee and Kentucky to the north, by Southern Americans. This as I mentioned above was the economic powerhouse driving the expansion of slave plantations and generating huge profits that fueled all sectors of the US economy OTL. ITTL if Southern US people are going to pursue similar opportunities they have to either emigrate to southern Louisiana and assimilate there as you envision northern US people doing in Ohio, or they will be tempted to seize territory from Louisiana outright. Assuming they are prevented from such filibustering, what impact do Southern Anglos have on southern Louisiana? Seeing the huge demographic boom the Louisianiens pull off, with that rapid population growth, it is easy to accept that the Anglos coming in at the north don't tip the cultural balance enough and that French prevails, eventually even in Ohio. What if there is a second stream of Anglos coming in though in the South?
Actually Anglos looking to make a profit as plantation owners might assimilate to French-speaking more easily than Yankee farmers. As somewhat pretentious people they probably have learned French already just for the prestige reasons, and their entourage at the plantations are likely to be locally hired (or purchased!) Louisianiens or French-trained slaves, respectively.