Slightly off topic, I remember reading a speech/pamphlet from the period prior to the Civil War in which an abolitionist (?maybe Lincoln?) drew on Russia for rhetorical purposes: the basic argument was that only the US and Russia were still maintaining slavery and that being in a same category as Russia was a bit off. There may have also been some suggestion that Russia was more 'honest' in its slavery... don't remember the basis for that however.
Yeah I recall something like that as well... And I also don't remember where I've seen it lol.
If France and Britain participated in the Civil War, it would have been a disaster for the Union as the naval blockades would have been reversed overnight. Furthermore, a second front opening in the North would have offset much of the Unions military superiority over the Confederates.
Offset, probably yes. Won? Who knows.
This part of the essay is relevant: "Bourne depicts the British predicament as their “defenceless” position in Canada, even with the help of the 10,000 additional regular infantry which Palmerston deployed in response to the crisis. (Bourne 211) A recurrent British fear was that their soldiers would desert to the American side, urged on by “crimps.” (Bourne 217). Their Canadian vulnerability, the British thought, encouraged Seward and others to twist the tail of the British lion. The US had the only serious warships on the Great Lakes, British fortifications were weak, Canadian volunteers were scarce, and there were few decent muskets for them. The greatest problem was that the Saint Lawrence River was blocked by ice in winter, preventing re-enforcements from reaching Quebec City by water; the only roads inland went dangerously parallel to the Maine border. Some of the British staff officers had to land in Boston and take the Grand Trunk Railway to Montreal.5 One is left with the impression that winter ice might have cooled Palmerston’s aggressivity even before Seward’s release of the captured Confederate envoys Mason and Slidell did."
So it appears that the British staff itself was not very impressed with Britain's military capabilities vis-a-vis United States at that particular moment.
I don't think the threat would have been very serious though as their were plenty of regional 'allies' to keep the Russkies tied up so Anglo-French troops wouldn't be needed that heavily.
Who would that be? The only ones I can think of are the Ottomans who might find it a good time for some more Russia-beating, but given that the Ottomans themselves were facing a million and a half problems during that time period, my bet is that they'd be happy enough that Russia doesn't touch them. I can't think of a single other power potentially willing to do the British bidding against Russia or the US at that time.