Not really. The US would still have the industrial power house of the North, the vast agricultural lands of the Midwest-Great Plains region to attract immigrants, and the huge mineral wealth the far west to feed the factories and financial sectors in the east. They'd also have vast potential for a large military that, while demoralized by the loss in the ACW, would be itching to prove themselves in a fight if anyone else got any uppity ideas of secession. One of the things Turtledove got right in TL-191, in my opinion. [1]
Economically the South always needed the North more than the North needed the South. [2]
It's also my opinion that in a situation similar to TL-191, where Britain and France ally with the Confederacy, the US would try to find a partner in the far-east, like maybe Japan or China, to secure the Pacific. [3] They'd also try to find a friend in one or more great power in Europe, perhaps Germany or Russia, or both(a reapproachment between the two isn't impossible; I've seen it in other TLs). [4]
1] If for purposes of discussion the CSA gets Kentucky and keeps Louisiana, the north is crippled in terms of trade. Sherman was right about that. Along with the Great Lakes the Missouri-Ohio-Mississippi River system controls North America. The USA cannot survive without controlling the outlets of those rivers to the sea...
2] Well, they HAD little industry of their own. But the vital need for those rivers dictated Round Two [5] coming a lot sooner than later.
3] China is chaos, and Japan is only one generation from opening their doors. They have a long way to go before they can help anyone.
4] Problem: The Royal Navy's supremacy on the high seas at the time was so preposterously extreme (even more than the US Navy's today!) that the combined fleets of the world couldn't help the USA.
5] A fact generally handwaved for purposes of discussion I admit.
Here's an alt civil war scenario that I like, the British help the CSA for whatever reason you can come up with including manpower and weapons, BUT...
This serves to infuriate the Northern populace due to, among other things possibly, the prolongation of the war and much more casualties. Eventually the US wins having just as large an army as they do IRL after beating the CSA. In retaliation they take enough of Canada with that huge army that the British eventually give up the rest.
The USA cannot win against the British Empire AND the Confederacy. Its just that simple. The Royal Navy breaks the US blockade and establishes their own on the US Eastern Seaboard. Canada's defenses are strong enough to hold off whatever forces can be spared from the Confederate Front until re-inforcements arrive from all over. Assuming this is a Trent Affair war (even Palmerston couldn't get intervention just for shits & giggles), the British have sufficient political heft at home to allow for a longer war, and sit back and wait for the USA to sue for peace when their economy collapses.
Meanwhile during all of the Civil war fighting, some Canadians resent fighting at all
No they won't, not at all. Canadians love to abominate nationalism. Until, that is, somebody actually disses their country [6]. Or invades it.
6] See the Gomer Pyle screwing up the presentation of the Canadian Flag during Game 2 of the 1992 World Series. Our friends to the North went nuts.
...in what they see as none of their affair while some others resent being on the side of the slave-holding CSA and refuse to fight in a war they oppose. This, on top of no or little British support due to them being stretched to the limit due to all of the global demands on their manpower, creates less military opposition when the US does eventually invade.
No. The Canadians see it as a matter of survival and their duty to the Queen.
Besides, membership in the Empire and meeting its duties was always part-and-parcel to the understanding that the whole of the Empire would be mobilized to save Canada from Yankee imperialism.
And that support would be coming. Saving Canada would be for Britain an "All hands on deck" moment for the Empire. No new wars against the Zulus, Afghans, Persians, or anyone else while this was going on. Any British prime minister who attempted to short-shrift the Canadians would be expelled in a Vote of No Confidence, if his Cabinet didn't collapse first. And remember, between the Canadians and British Army, they would only have to
hold the line while the Royal Navy won the war.
Post civil war this creates a huge gap between the British and the US. I wonder on what side the US would fall when WWI and II happens in this scenario.
Assuming the alliance of the French, British, and CSA leads to a quick American defeat, and the reasons for European Intervention were not Trent-related but more imperialist in nature, with the CSA going as OTL until Intervention occurs? Assuming no USA dissolution, and if the USA completely abolishes Slavery and war breaks out in a ACW 2 the 1870s? No second foreign intervention by a Third Republic France and post-Great Reform Act of 1867.
Leaving the situation that of a re-united USA with a Reconstruction period possibly lasting into the 1890s. And the US seeing France and Britain as their bitter enemies going into World War One. Uh oh...
As a possible POD, maybe the US does at least a little better in the war of 1812, not winning any territory in the end, but prolonging the war and forcing the British to commit resources they desperately need elsewhere. This causes the the Brits to lose one or more battles they should have won. This pisses off the British quite badly for quite awhile afterward, because many of them blame the US for their losses.
Impossible. The US Navy was too tiny to win many "victories", sinking frigates. If the British hadn't played the expectations game so badly (fir-built frigates), they wouldn't have been embarrassed. And once the Napoleonic Wars ended, the British were in the position of exacting major payback.
In between the war of 1812 and the Civil war the tensions mount between both sides because of the British impressing US citizens and ship/sailors as well as raiding of a US port/settlement or shipping convoy under False or Pirate colors with the US finding out anyway. Then along comes the Civil war and viola.
I know it's full of holes but, whatever I'm tired and don't care.
Acting this way in the Age of Steam would be setting a dangerous precedent for Britain's usual enemies on the Continent. It was THEY who were by this time pushing for the freedom of the seas more than anyone, and only individual sea captains who were going off the rails.
Another scenario, the Brits help the CSA win the war. There is strong revanchist feeling in the US as a result. Military spending is considerably higher in this TL than OTL and it allies itself to Russia just after the war and Prussia\Germany in the 1870-1880s. It takes the US until the 1900s to be where it was in the 1880s OTL. WWI breaks out where it is the US/Germany/Russia/AH Empire vs. GB/France/Italy/Turkey/CSA. The US takes all of the CSA and all of GBs and France's American colonies and maybe a few islands in the Pacific. Russia takes GB and France's colonies in Asia and Constantinople. Germany takes parts of France and Italy plus some African colonies while AH takes parts of Italy and Africa.
I think the Entente would sue for peace long before this scenario ended. Also, I repeat: Round Two doesn't wait this long for the CSA/USA. I rarely see a serious explanation for why not?