I worded it poorly. What I meant is that even after the implications of a drastic change in the geopolitics of the Western Hemisphere, the Napoleonic Wars, nationalists in colonies, and Presidents are elected as in OTL even after different presidents are elected before them. That's Turtledove AH. Admittedly, it does finally begin diverging properly after the Congress of Vienna, but that's still some forty years after the stated POD.
Well, you may notice that major divergencies about the USAO/VLR Presidential sequence start accumulating since 1800. However, many of the usual names still turn out because the vast majority of the early US leaders rose to prominence during the Revolution and American Canada by itself is not going to change the rooster of Founding Fathers substantially (besides adding an handful of extra members, like Carleton). In one TL, divergencies really start hitting Europe in 1814, in the other, in 1805 (but start building up in 1784). That seems wholly plausible to me, since the Americas and Europe were still fairly separate parts of the world in late 18th century. Frankly, I do not believe in highly chaotic theories of history.
And many events seem to be given minimal amounts of details behind them. Why does Nova Scotia rebel in the first place? All you say is that anti-British agitation has spread to it. There are no details to it. You just handwave it. There's no clear reason why the anger spreads. Was there some kind of oppression or injustice performed by the British? Was there some inspirational local leader? Were more pamphlets distributed?
The explanation I currently espouse is the one given in VLR: the British Parliament punishes the colonies for their agitation by awarding the Ohio Valley to the HBC as part of TTL Intolerable Acts. This makes NS as restive as the other 14 colonies. Later, Jonathan Eddy's expedition ITTL succeeds in bringing most of NS (but not Halifax) under Patriot control because it gets more support thanks to Patriot Canada. The rest is taken care of in the peace treaty.
Or the British-Patagonian War. Why are the British attacking Spanish settlers? Are they just cruelly lashing out? Is it because Spain is a client of Napoleon in Europe? Was it some kind of rogue action by an overzealous officer?
You may or may not be aware that even IOTL, there were British
attempts to conquer Rio de La Plata in 1806-07. My basic assumption is that because of the loss of Canada, those British efforts ITTL get somewhat more support (and hence are successful) as the attempt to rebuild a colonial empire in South America.
The US was historically lucky. In both timelines it stretches its luck even more. The Great Powers, particularly the UK, are not likely to just standby and let the US take over most of the western hemisphere without some kind of reaction.
The creation of British South America, which spans Argentina, Uruguay, Paraguay, Chile, and southern Brazil, seems a rather substantial reaction to me. Another divergence caused by this is British seizure of most of Indonesia. ITTL America wins the War of 1812 because of much better military preparation, a more favorable strategic situation, and British defeat in the Napoleonic Wars. Therefore, a sphere of influence delimitation about Latin America is defined between US and UK in the peace settlement, with the British Empire controlling the southern third of South America, America the northwestern third, and the Brazilian third remaining independent and neutral but leaning towards the UK side. Mexico is likewise acknowledged to be neutral but loosely belonging in the US sphere of influence.
Even if it feels like the stronger side, caution spawned by losing two wars in North America in a row, and the distraction from the continental Europe hegemons being rival to Britain, make it so that the UK does not feel like risking another major war with America if it can avoid it in 1816-1858, even when America goes to war with Mexico. It deems BSA enough and focuses on expanding the Empire in Asia, even if US-UK imperialistic antagonism abouth the Western Hemisphere lingers (moreover, after the carnage of the Napoleonic Wars, the great powers experience lingering weariness about new major wars for a generation or two). When the unique historical opportunity to break up American power shows up with the Secession, Britain is quick to seize it and it intervenes in the ACW. However, their continental rivals do the same, and everything goes downhill for London and its *Entente allies from that.
The US manages to win consistently over the UK and France for no clear reason until perhaps the Civil War.
America essentially won the Quasi-War even IOTL, and ITTL the Franco-American War is just the slightly expanded, declared version of it, with a couple successful US amphibious landings thrown in. As it concerns the War of 1812, the TL strives to explain how political divergencies lead to a much better US military preparedness in the War and the creation of strong political links with many Spanish-American independence leaders. Even IOTL, USN performance was rather good, and TTL builds on it. Moreover, American Canada ensures that ITTL America only has to focus on defending its coasts, fighting for naval parity in the Caribbean theater, and providing support to its Gran Colombia allies (which provide local support for US landings in turn). In the meanwhile, Britain keeps being distracted by the Napoleonic Wars, which it ultimately loses, and is also busy entrenching its control over southern South America. All of that adds up to a decisive US victory.
It had some four or 500 years of history behind it. Fifty years is not enough to overturn generations of racism and ethnic cleansing on the frontier. 150 hasn't been enough even now.
ITTL America does not suddenly go for Politically-Correct multiculturalism and leaving the Indian tribes alone. It just shifts from blood-based exclusionary (and genocidal) racism to cultural assimilationism. It adopts the idea that "civilized" Indians which embrace American culture and lifestyle and do not mess with American settlement may be US citizens in good standing. IOTL Washington was an assimilationist. The divergence of the Iroquois fighting for the Revolution makes it so that assimilationism becomes the mainstream viewpoint. This leads to a patchwork outcome for the Indian tribes: the ones that embrace American culture and do not forcefully resist American settlers get assimilated: the ones that refuse both suffer a similar fate to OTL. Racism does not disappear, but its given a rather different bent, which ultimately provides a less dystopic outcome.
And if "civilized" assimilated Indians may be accepted, it also means that racism towards mixed-bloods and Indians in the former Spanish colonies is much more toned down, since those peoples are already assimilated to a "Western" culture and lifestyle by Spanish colonialism. And since Catholic French-speakers were at the forefront of the Revolution and became an integral part of America, there is no outstanding prejudice towards other Catholic Romance-speakers. Once such prejudices are lowered, US elites can look at the educated Creole elites that control the political system in the former Spanish colonies and recognize that they are not that much different from Southern gentlemen. This breeds their acceptance as peers.
There is also the fact that ITTL the meme spreads early of republican brotherhood between the US and the former Spanish colonies. Strong political ties are forged between American leaders and the Libertadores before, during, and after the War of 1812 and the Spanish-American Wars of Independence (wrapped into one ITTL). US support is given to Latin American patriots and US volunteers and soldiers fight in South America. This forges the idea that the American Revolution and the Spanish-American War of Independence are two sides of the same coin (reinforced by UK conquest of BSA). Simon Bolivar is widely acknowledged to be the same ilk as the Founding Fathers (and many Libertadores become pro-US). From that, it is a relatively brief step to accept that former Spanish colonies in the US sphere of influence belong in the USA.
Well, that's why I thought it wasn't meant to be fully serious, its more a story instead of a history, if that makes sense.
Actually, I fail to see the difference. The story is wholly serious. USAO is an earnest AH challenge exercise about "how could modern superstates that resemble 1984's Oceania and Eurasia be created that are no more dystopic, possibly slightly more utopian, than OTL democracies, in a plausible way" ? Of course, it does not pretend to be perfect. Like the experience of his author, it grew in the effort, and as matter of course, the creative effort of VLR already revealed several ways about how some details ought to be changed, or provided better explanations and justification, than the original. But the suggestion that it is not earnestly serious, some tongue-in-cheek thing, is somewhat annoying for the author.