A map of a perpetually-unfinished TL of mine called
Baseball, Poutine, and Apple Pie, loosely inspired by
@Glen's
Dominion of Southern America TL, in which Canada joins the American Revolution but some of the Southern colonies remain loyal to the Crown. This is specifically a linguistic map of the United States in 1983, shading each of the 42 states by the predominant language spoken within. The gist of the TL is that the US didn't just absorb Canada, it "became" Canada writ large, specifically the stereotypical version thereof, and at the center of that is American multilingualism, starting with the unique position of the French population but also including Germans and Chinese later on.
The PoD, as in
Dominion of Southern America, is that Guy Carleton, 1st Baron Dorchester is never appointed governor of Quebec. In OTL, he followed the lead of his predecessor James Murray and was conciliatory with the French population, making many compromises and agreements with them that culminated in the Quebec Act 1774. This ensured their loyalty to the Crown during the American Revolution, or at least their acquiescence to British rule. ITTL, however, the British merchant community in Quebec, which had grown disaffected with Murray's rule, got a governor more favorable to their interests, one who accomplished little except to radicalize the French population. Instead of a Quebec Act, we get
Patriotes attending the Second Continental Congress and signing the Declaration of Independence.
Without a northern base, British positions in the northern half of North America collapsed as Nova Scotia followed Quebec and the British base at New York City was besieged. A change of strategy soon followed, and the British sought to instead strike at the "soft underbelly" of the revolt: namely, the southern colonies, where Loyalist sympathies ran strongest. The second phase of the Revolution began as the fighting moved south. Reestablishing Loyalist governments in Georgia and the Carolinas, the new frontline was in Virginia, where it remained until the war ended around roughly the same time as OTL, with Britain suing for peace as half of Europe geared up to intervene on the American side. The Peace of Paris in 1783 ended with the British in control of the Carolinas, Georgia, and the Floridas in the south, along with Newfoundland, Labrador, and Rupert's Land in the north, while Spain regained Louisiana.
History happened. While many Acadians in Louisiana were happy to live under a Catholic king and had already built new lives for themselves, a few thousand accepted invitations to return to their former home. Trenton, New Jersey became the US capital thanks to its central location. The failure to acquire Labrador and Rupert's Land in the treaty rankled the Canadiens and caused them to stick with the American project rather than split off to form their own nation, especially with TTL's version of the First Amendment enshrining freedom of language alongside speech, religion, the press, assembly, and petition. TTL's alt-War of 1812 started thanks to the Montreal-based North West Company's continued violations of British sovereignty in Rupert's Land, on top of concerns about impressment of American sailors, but with Rupert's Land essentially defenseless against American attack and the militias in the warm southern parts of British North America not all that eager to leave home, the UK had little choice but to surrender the thinly-populated northern lands at the peace table, retaining only the island of Newfoundland. As Spanish rule in North America collapsed, a compromise was forged in Louisiana, with the Americans and the British, each eager to keep the Mississippi out of the other side's hands, establishing a neutral independent republic south of 36°30' north while the Americans claimed the land north of that line.
The end of slavery (and the seigneurial system in Quebec) happens relatively peacefully in the 1830s and '40s, but instead, religious conflicts gripped the young nation during that time. Without a national border separating it from the rest of the US, the Second Great Awakening arrived in force in Quebec, where the Catholic Church's authority was already in decline amidst the US' liberal political atmosphere and the booming North West Company was becoming a haven for young Canadien radicals eager to escape their conservative homes and see the world. When the government of Quebec attempted in 1842 to crack down on the "new churches" and shore up the power of the Catholic Church, the Protestants in New England responded in kind, forcing the US government to step in and prevent the sort of war between Massachusetts and Quebec that the Constitution was designed to prevent. The legacy of the "Quebec crisis" was to further underline the separation of church and state by incorporating the Bill of Rights' protections on civil liberties and extending them to state and local governments, enshrine a culture of strict government neutrality on religious matters and suspicion of political religion be it Catholic or Protestant, and provoke an exodus of Nephites (TTL's alt-Mormons) to OTL's Alberta as both the Catholics and the Protestants decided that, while freedom of religion is cool and all, plural marriage and adding new books to the Bible are bridges too far.
All in all, it was a more peaceful outcome than the end of slavery in the British colonies, which revolted against the Crown in 1853 as abolitionists in Parliament attempted to finally crack down on slavery in the colonies. In the US, sympathy for the abolitionist cause outweighed any desire to "finish what was started" and reclaim the three southernmost colonies, and while a few private citizens in Virginia, Maryland, and Kentucky, still bitter at losing their slaves, did offer aid and comfort to the rebels in the "North American Confederacy", far more formed the thirty-thousand-strong "Spartacus Brigade" and fought alongside British soldiers even as the US remained formally neutral. When the government of Louisiana, fresh off of annexing the breakaway Mexican state of Texas, declared open support for the NAC, the war expanded west as the UK declared war on Louisiana, with Trenton's tacit approval (secured by letting the US annex another breakaway Mexican state, the pro-American Republic of California, and the promise of a treaty permitting free travel along the Mississippi after the war). Mexican protests were muted when both the US and the UK agreed to very favorable settlements of border disputes in the annexed territories in Mexico's favor, including in the Rio Grande Valley and the Los Angeles Basin, with more than a bit of an "offer you can't refuse" to the whole deal as both parties insinuated that, after the Planters' Rebellion was settled, Mexico would not be able to press its luck any further.
Where westward settlement was concerned, the Quebec diaspora, the survival of large Indian and Metis populations (the North West Company lobbied hard against the ethnic cleansing of their profitable business partners), and constitutional protections on freedom of language caused much of OTL's Canadian prairie to become Francophone. Industrialization also brought the Quebec diaspora into the mill towns of New England and the industrial cities and mining towns around the Great Lakes; Sault Ste. Marie, Duluth, Pawtucket, Fall River, and New Bedford are all majority Francophone cities, and Chicago, Milwaukee, Detroit, Portland, Worcester, and Providence all have substantial French-speaking populations. Anglophone Yankee settlers predominated south of the Great Lakes as well as in southwestern Ontario (Toronto is considered the "border" between English and French in the state of Ontario), such that, despite the presence of bilingual populations on either side, the Great Lakes are sometimes called the "American Channel" for serving as the "border" between Anglophone and Francophone America.
Immigrant communities also affected the linguistic makeup of the US as time went on. Most of the Irish already spoke English coming into the US, to the point that even in Quebec itself the Anglophone minority contains a lot of Irish speakers, while the Germans came to the Midwest in such numbers that their tongue came to be seen as America's third major language, with even the non-German-speaking Scandinavian immigrants learning it rather than English or French. Unlike the French, the main centers of German immigration were also heavily settled by Yankees, and over time German became a minority language in every state where it was spoken; even in Minnesota, Iowa, and Nebraska, the heart of "Neu Deutschland", Allophones make up only about 40% of the population by 1983. The German-inflected Midwestern accent, however, is as thick as bratwurst. (Picture
Fargo, exaggerate a bit, and you have a good idea.) Finally, out west, the Chinese also left their mark. While the Chinese language never acquired the presence of even German, on the West Coast it is widely spoken by the descendants of Chinese immigrant communities.
Of special note are immigrants from the Latin world. For a variety of historical reasons, the Italians, the Portuguese, the Cubans, and the Dominicans were as likely to learn French as English, even when they landed in Anglophone cities. First, it was plain easier for a speaker of Italian, Portuguese, or Spanish to learn another Romance language than a Germanic one like English, in a process that saw American French in turn adopt a great many loan words from those languages. Second, the Catholic hierarchy included a lot of Francophone Canadien priests even after the arrival of a great many Irish Americans into the priesthood, and the Church became an incubator for the French language in immigrant communities across New England and the Great Lakes wherever the Quebec diaspora had any significant presence. Third, in New York specifically, the merchants of the North West Company formed a small Francophone community as they gathered in America's largest city to sell their wares, and more broadly, America's merchant classes spoke both English and French in order to trade across the Channel more effectively. Finally, in the case of the Italians specifically... yes, the Mafia was a factor. Knowledge of both English and French became a necessity in organized crime as their own trade routes crossed the Channel, and furthermore, speaking both helped gangsters evade clueless, underpaid police officers who knew only one. (Federal police in the 20th century very quickly learned the value of multilingualism in busting the Mob.) The result was that the New England dialect of French became the East Coast dialect as it spread to New York, Syracuse, and Newark and grew more entrenched in those parts of New England and the Great Lakes where it was spoken.
At the same time, as the federal government expanded in the 20th century, French expanded even further south to Trenton, DC as Francophones arrived for government jobs. With New Jersey already home to its own Francophone community centered on Newark's Italian and Portuguese communities, once suburbanization came the French in Trenton overwhelmingly settled on the Central Jersey side of the Capital Beltway, knowing that New Jersey was more accommodating of the French language than largely Anglophone Pennsylvania (where even the Italians in Philadelphia and Pittsburgh, without the hook of the Canadiens or New York's trade, wound up speaking mostly English). The growth of mass media mid-century hastened the assimilation of immigrant communities into either English or French, the two major language groups that could field their own national radio and television networks. Only the Germans and Chinese were able to resist assimilation, and even theirs are chiefly regional languages that are widely spoken only in parts of the Midwest and West Coast respectively, as opposed to languages with near-national reach like the Big Two. The Athabasca tar sand, uranium, and rare-earth mining boom in the late 20th and early 21st centuries caused a notable expansion of English into the far north, as communities that were once dominated by Metis and Canadien farmers and hunters were now filled with thousands of blue-collar workers from all points in the US, including its Anglophone parts.
Language politics in the US have always been fraught, with both Anglophone and Francophone politicians and writers on either side of the Channel constantly fretting about protecting their language from the uncivilized brutes on the other side. Historically, Anglophone populists have treated French as the language of superstitious Catholics and violent gangsters, and their Francophone counterparts have done the same with English as the language of elite fat cats and bigoted Protestants. There's also a subset of nationalist, Anglophilic English speakers concentrated in elite institutions who dismiss American multiculturalism as its greatest weakness, the reason why it has always remained so dovish rather than "taking its place" as a world-straddling superpower, and think that the US needs to be more like the United Kingdom and the Dominion of Carolina, what with the British Empire still being the world's preeminent superpower in 1983.
However, in the face of America's world-class standard of living, its vast breadbaskets and fisheries, its legendary industrial prowess in everything from hybrid cars to "winter-proof" trucks to nuclear reactors to fine fur coats, and its soft power and international respect for its commitment to the Council of Nations' peacekeeping operations (without obvious avenues for imperialism in the Caribbean and Mexico in which to dip its toes, the US largely stayed on its home continent), most Americans have long since concluded that there's nothing wrong with multilingualism. It has become the root of many of the country's famed liberties, as conservative and reactionary forces were often too divided along linguistic lines to mount much resistance against "America's natural governing philosophy" of liberalism, embraced in various forms by the Federalists (in the Hamiltonian tradition of a strong central government and an emphasis on development and industry) and the Democratic Republicans (in the Jeffersonian tradition of an economically empowered citizenry and an emphasis on small business and later cooperatives). Plus, knowing multiple languages has always been known as a mark of refinement and intelligence, which means that there's a reason why the nation where doing so is a fact of life in the vast "bilingual belt" is also a world leader in advanced technology and electronics and home to some of the world's most elite universities.
Besides, it's worked for over two hundred years, so why give up a good thing?