Ok let’s begin with the possibility of union. That was in 1800 not 1784. Plus the comparison of Ireland to India is misdemeanor becUse we talking about a union across Atlantic. If the difference is loosing them to the US or union I think there will be a movement to keep them British.
I said nothing about not remaining British. In fact, if you bothered to read, you'd see I offered
reasonable suggestions of British actions to keep them British. Political union across the Atlantic before about 1830 (when
Royal William makes her transit; I don't count
Savannah, which spent most of the transit under sail, not steam) is about as credible as the U.S. today suggesting a political union with the Moon.
That was the reason for the union of Canada.
It's a rather different thing to build a railway to unite land territories than to project power across an ocean.
is the US the only one that progresses?
I never claimed it. The British response must be
reasonable. There's a very well-researched (& -written

) thread here about an Anglo-American war that very clearly spells out the difficulties. I suggest you seach for it. (I'm embarrassed to admit, I can no longer recall even the thread creator.




)
I am saying that 75-100 is a huge amount of time and we not sure how BC will progress.
Fair point.
Will it more more British?
I would tend to doubt it.
Will the people in BC have any desire or need to join US? The reasons they joined Canada was for the railway. Here we just get short railway connecting Seattle to Vancouver. Is that worth joining US? Be controlled by another country while you can be your own country?
Seriously? In 75-100yr, & with a Gold Rush in play, you think there would be no U.S. "immigration"? And you think BC is going to stay its own country in the face of overwhelming numbers of Americans chasing gold? (Before that, would the U.S. bother with annexation? Maybe not; I'd give it about even money. Your notion of Britain flooding BC with East Indian settlers is up there with Canada invading New York.

)
As for Califórnia snd Texas. Would the Americans who settle there desire to be part of US or be independent countries. They were both independent prior to joining. Would they join or would they decide they wAnted to live in different country?
They did desire separate countries. Neither could make it work. Desire alone doesn't get it. The U.S. population was such it could overwhelm the opposition. (Just ask the Apache, Sioux, Cheyenne...)
The reason that IMO it develops the same way is because they were formed by American settlers who wanted to be a part of the US from the start. Texas would want American protection from Mexico. The California Republic, despite having an amazing flag, was very small. IIRC it controlled one city before America came and absorbed them. Besides, California and Texas had MUCH smaller populations then.
Correct. In fact, IIRC, they both amounted to locals producing excuses
to be annexed, not to remain independent. (Thx for reminding me.)
Please don’t say everything going to be same because it won’t.
I'm not. I am saying it must follow reasonable pathways, unless the express goal is to examine a longshot or a particular situation. Even then, reasonable extrapolation
after that is wanted. (Again, unless the writer is expressly saying handwavium remains in play.)