I would like to tell you about a country called New Britannia. In a world where the concerns and interests of the Thirteen Colonies were given considerable weight in British political discourse, New Britannia stood as a shining example of successful colonial governance. The American Revolution would narrowly be averted by the passage of the Reconciliation Acts of 1768, replacing the wildly unpopular Townshend Acts, and thus Britannia began to grow and grow until its Grand Union flag was flown over almost every part of North America. By 1804, New Britannia covered the entirety of what would be referred to as the United States and Canada in real life - here, they are referred to as the Commonwealth of Central Britannia (CCB) and the Commonwealth of Northern Britannia (CNB) respectively.  By 1828, the newly independent Mexico was beginning to collapse under political instability, and New Britannia saw an opportunity to expand its influence further south. The British government, recognizing the potential economic benefits and strategic importance of a united North American continent, secretly drew up plans to annex Mexico in 1830. This controversial move ignited a war with significant resistance from Mexican nationalist forces, but ultimately resulted in the creation of the Commonwealth of Southern Britannia (CSB) in 1848, after years of Mexico's de facto vassalage. New Britannia's rapid expansion raised concerns among other global powers, particularly France and Spain. To maintain stability and avert potential conflicts, the Great Powers Accord was signed in 1853, recognizing New Britannia's right to influence over the entire North American continent and establishing it as a self-governing dominion within the British Empire. Spain would sell Cuba and Porto Rico in 1877 and would later sell the Philippines in 1898. New Britannia was quick to pounce on Panama when it split from Colombia in 1903, and the Panama Canal was built to facilitate the passage of cargo between the Atlantic and Pacific in 1904. They would all be integrated as commonwealths. The overseas commonwealths, as well as the CSB which is situated on mainland North America, would see significant economic development and modernisation, but the architects and beneficiaries of this were largely the British elites and their allies in New Britannia. The commonwealths became reliant on British investment and trade, with the majority of their resources and profits flowing back to the empire. The local populations, while benefiting from some economic advancements, were often marginalized and had limited political power. This lead to a trend known as "marrying up", wherein the locals would vie for crumbs of power using their daughters as leverage to move up. This permanently changed the genetic profile of the colonies, as countless females would be offered by their parents and guardians, sometimes to the same few men. In a generation, the offspring of these elites (the creoles as well as those fully European) were a major force in these colonies. Many local families would resort to extreme measures to ensure they had a chance at moving up in colonial society. This included the infamous infanticide against males to such a scale that for instance, in the Commonwealths of Cuba and the Philippines, the local economies and workforces were decimated, with extreme gender imbalances seen amongst the locals, to the point creole males were some of the only males that survived into adulthood. As a response to the wave of infanticide, it would become a capital offence, although few witnesses would cooperate, as most were either sympathetic or afraid of reprisal. With the damage already done, Europeans would begin to flood into the commonwealths to fill the labor void left by the decimation of the local populations. In doing so, New Britannia also found itself with loyal subjects who were more closely aligned with British culture and values, further solidifying its control over the colonies.
As far as basic information goes, its capital is Philadelphia. This is part of the state of Chesapeake, which obviously includes Pennsylvania but also includes some of the other core provinces such as Virginia, Maryland, Delaware, New Jersey, and New York.

For these reasons, most (let's say colonies to differentiate the CCB and CNB from those that were not predominantly British) colonies have significant European admixture, and though such apartheid systems have officially been abolished, some of British descent still hold significant power, and those of British descent form not only the largest groups in the CCB and CNB where the legend of New Britannia all began, but also in colonies. For instance, 43% of the population in Southern Britannia possesses 25% or more British ancestry, while 32% of the population are Britannians. This grows to 63% and 48% in Cuba, 71% and 52% in Porto Rico. The first number also overlaps with other groups, obviously.

Britannians are the predominant ethnic group in New Britannia. They are English-speakers of Northwest European heritage, unsurprisingly most of this is British or Irish with smaller numbers from Scandinavia, Germany, and the Low Countries. They are also known as "Americans." They are present in large numbers just about everywhere in the realm.
Acadians are a smaller group of predominantly French speakers, present mainly in Maine, with larger-yet populations in the American South (Cajuns) and Pacific Northwest (Cascadians.) A significant amount of Acadians also came to the South and Pacific Northwest from Italy. There are Italian Acadians, French Acadians, and mixes of the two. 22% are native Italian speakers while 67% are native French speakers, and in areas with a similar climate to France and Italy, you can see a similar romantic and outgoing culture that contrasts with the larger Britannian culture.

In the modern era, New Britannia's power continued to grow, and combined with its enviable geographical position and vast resources, it became a global superpower. With a mainland featuring most of North America (Note: really just the United States, Canada, Mexico, and the exclave of Panama), it's the world's largest country by land area, and the Americans are quite proud of this.

Cuisine: Britannian cuisine is heavy in meat and potatoes. Regional variants exist, but this is largely consistent.