Ireland! There are a variety of ways to get a United Ireland. Brian Boru is the classic.
You already had Irish monks operating on Iceland before the Vikings arrive. The Papars, if I recall correctly.
From there you just follow some combination of the Viking/Scandinavian and English colony...
https://en.wikipedia.org/wiki/Wang_Cong'er would be my vote. While it's unlikely that she'd end up in any position of authority, let alone empress regnant of China, I find the slim possiblity intriguing
Maybe after the Congress of Vienna, France needs to be punished a little bit more for reasons. French Guyana is awarded to a Hanover. Near enough British Guyana to get support, but separated by Dutch Guyana, so less likely to become a defacto extension of the British colony
Here's my attempt:
* war of 1812 or similar - new england breaks away and becomes British protectorate. Louisiana also become a British/Spanish condominium (but de facto British). Tecumseh's federation survives as British protectorate. This would be a devastating loss for the USA, but it is...
I think most people on this site will say that it is very unlikely that the US would actually end up annexing all of Mexico. Most Americans at the time would not want to share the country with a bunch of spanish speaking catholics. This usually results in the suggestion that the US would only...
As for the question of American settlers in British Louisiana, I think the situation varies here as well. We have two primary examples, Texas and Ontario. In Texas American settlers eventually broke away and joined the US, in Ontario they ended up mostly content as British subjects.
I think...
I think some authors and readers need timelines to be at least somewhat likely in order to engage with them. Others only need them to be at all possible, regardless of likelihood.
Prioritizing the first perspective makes absolute sense from a narrative perspective. Prioritizing the second make...
Lists like these would probably be a good place to start:
https://en.wikipedia.org/wiki/Category:Heirs_apparent_who_never_acceded
https://www.mentalfloss.com/article/654563/royal-heirs-who-died-before-they-reigned
There are also rebellions and revolutions that failed. The leaders or otherwise...
There are a couple of examples that come to mind:
Henry Cavendish discovered tons of things in the late 18th, early 19th century. But he was so socially reclusive most of his discoveries had to be rediscovered by other people later
Vacuum tubes were invented not too long before the transistor...
Building on that, it could mean that when evolution is experimentally verified later, some people could interpret that as also supporting Marxism/socialism/communism. People often have trouble unbundling ideas
It seems likely that a plausible story could be told where that happens. Another factor that could be useful might be Andrew Jackson dying in New Orleans.
As a storyteller your job would be to ensure that the right people encounter each other at the right time having heard the right news all...