Subscribed to see what a Red Britain looks like when the dust settles.
I'm afraid I don't have any specific insights into how the domestic dynamics would play out during the 1920s.
Colonial issues--starting with Ireland and India of course--will be huge.
It's my impression that Britain itself has plenty of potential members of an organized far left party. But also lots of conservatives of various kinds who in this case would pull together; it would be a knock-down fight at a time when all of Europe is reeling from the battering of WWI.
Canada I suppose would come under US hegemony, the question is, how far. Would there be a Canadian republic, which would be drawn to federate to the USA? More likely, it seems to me, if the Right in Britain is defeated, the Royal Family would flee overseas and Canada seems the obvious place they'd head. Under these circumstances the USA, if it remained largely as OTL, would welcome and facilitate the settling of what remains of the authority of the British Empire under their wing, so Canada remains a Dominion and there is no question of union with the USA--but de facto, the "Empire" is under strong US influence as a whole.
But will the USA remain unbutterflied? OTL there was panic enough about domestic leftism, the "Red Scare" and "Palmer Raids." It took the pretext of WWI and the principled opposition of the American Socialists to joining the Great War to shut up people like Eugene Debs. And despite the fact that most leaders of the postwar hard left, mostly associated with the Communists, were indeed of foreign origin, I think there was real fear American workers might be won over en masse to a radical program. Actually of course there were already a lot of American-born radical leaders, but these had been largely locked up or otherwise broken in the WWI crackdown. The fear was if the tide turned too far, all the radicals who hadn't actually been killed would join forces and America might undergo a radical shift.
This was OTL, when the most inspiring examples of labor success were first in Mexico then in Russia. If the far left could take over and stabilize their control in Britain, I'd think the panic of the American Right would have been far worse. But too many excesses in trying to suppress "unAmerican" thought could be their downfall, too many Americans might well think "who are you to say what 'American' is, and what have you guys done for me lately?"
If the resurgent American left can join forces with African-Americans and convince them the post-revolutionary leftist regime will not be racist, and convince large numbers of Southern (and other whilom racist) white working people that their interests were best served by a post-racist proletarian society rather than clinging to their Jim Crow symbolic privilege, I'd think it would be Game Over for American capitalism at that point, unless the leftists then ran things very badly afterward.
So there might not be an Uncle Sam for the exiled British Monarchial Empire to kowtow to!
Meanwhile, is it a certainty that the British Monarchy will fight the British Left to the bitter end? Is there a possibility that at some point in the struggle, the British system, ever attuned to the possibilities of compromise and muddling through, would arrange for a conditional, more or less constitutional surrender? That is, the Labour Left is suddenly treated as legitimate, allowed to take control of Parliament, expected to argue its sweeping program not just before remaining conservative opposition in the Commons and the Lords, but also in law courts? And some member of the Royal Family, if the current monarch is not acceptable he steps down and some more "with-it" successor steps up as King or Queen, so the monarchy remains?
That seems like a very British outcome to me; it might leave a lot of diehard British conservatives seething but serve to mollify or at least quiet others who go along more or less grudgingly.
But back to the Empire; first of all will the Irish, at this late date, accept a continued association with the British Empire (or "Worker's Republic," whatever!) if it means being part of a radically progressive regime, with autonomy presumably? Will a Worker's Britain even care about keeping Ireland within the union somehow? (They ought to, just for strategic reasons, unless they are very very confident no reactionary foreign power will ever be able to seduce or leverage Eire into being a stepping stone for attacking Britain itself). Will the revolutionary movement accept the risks of a free Ireland and position itself behind simply letting them go, thus further polarizing the right against them?
Meanwhile India is trying to tear loose and the Imperial structure that stands against that is being toppled at its base; presumably India rips loose in the 1920s even if the the LabRads are ultimately checked and crushed. The whole rest of the non-white colonial Empire must shake with that defeat.
Meanwhile the funding for institutions like the Royal Navy is in grave doubt and soon not forthcoming at all. But to what degree are the naval crews themselves subject to radicalization? On the whole I'd expect the RN discipline to suppress radical mutiny, but might it be different if the issues being fought out in Britain hit close to home among the sailors? Might the officers too include a few willing to change sides and join the revolution?
Again the monarchy and the moderates in Britain cutting their losses and making their peace with the rebels might play a huge role here. But the RN will definitely have a much cut budget and slashed personnel, I daresay at least a few ships will mutiny toward the Right and make port at some rival power's docks, offering to sell the ship in return for crew getting asylum in the other power's navy.
In the 1920s though, that means either the USA is holding on the right and gets all these defecting RN elements, or who else can they offer their services to? Just Japan or France, and I don't think RN crews will be comfortable merging into either nation's ranks. They might still sell the ships, and make for a refuge--but where?
While I suppose Canada will remain moderate-conservative assuming the USA holds as OTL, I'm not sure about Australia and New Zealand. They might quite happily join a Worker's Commonwealth with revolutionary Britain.
South Africa on the other hand might wind up being the place all the reactionaries go, if Canada is not safe for them, and so the "British Empire" might boil down to a number of radical former "white" dominions, a bunch of recently self-liberated former colonies in Asia now in the balance between a sudden, ill-prepared independence (one where they might be offered the option of a partnership with Worker's Britain and its Labour Commonwealth) and a reactionary African Empire based in Cape Town trying to hold on to the African Southeast coast up to Kenya and Uganda via white supremacist settler regimes--without the support of the world-spanning Empire, but with the demographic boost of a bunch of right-wing refugees from around the former Empire. I'd think they could stay in control for a decade or so, but either they keep their part of Africa primitive and poor, or they raise up a native working class they ultimately will not be able to rule who will kick them out eventually.
What I'm hoping to see is the somewhat muddled result of Britain still remaining a nominal monarchy, with a Windsor King or Queen, and the Empire still existing in some reduced form as a Worker's Commonwealth, with Australia and New Zealand as core members along with Britain, and much of the former colonial possessions, India and Ireland among them, being allied in common economic plans and common defense; meanwhile a number of diehard British conservatives have seceded and set up their own rival Empire, perhaps they have some renegade member of the Royal Family to call their new King, disputing the right of the Labour regime to exist and intriguing with leftist Britain's enemies.
And the USA can be anywhere--holding firm as a reactionary power cynically scooping up whatever debris falls out from the Empire's convulsions, itself plunged into a decade of civil war of great savagery and unclear outcome, or itself switched over to the left, as was possible I think. Canada's status will mirror the USA's--if the US remains conservative, Canada will be the core of the anti-Labour Empire and home of the rival monarch (or just the monarch if Britain winds up rejecting monarchy itself). If the US is in doubt Canada will also be insecure and unstable and badly shot up; if the US goes left then Canada will stabilize on the Labour Commonwealth side of things.
At this stage in history I don't think any foreign powers are in much of a position to mix in too much, except insofar, as I've considered for the USA, they are themselves in danger of major civil overturns--as France and Germany certainly would be. Assuming they try to just sit these upheavals out (and I'm not sure Weimar Germany possibly could, dependent as they were OTL on US patronage and goodwill in the 1920s) I don't think France would dare go for immediate land grabs of Britain's colonial possessions--these are too likely to be poison pills, infecting their own colonial armies with radical dissent. It would be different if the colonial governors of various possessions offered to deliver their colonies over to French protection wholesale, and were keeping order well enough to make their "title" seem good. But that wouldn't be French aggression so much as British treason.
Similarly I don't see Italy being really in a position to do anything too rash without fearing risking bloody consequences.
And the Bolsheviks in Russia would of course be generous with commentary and advice--not all of it positive, they'd probably skewer most of the factions in Britain as some kind of traitors or other to the Revolution--but would hardly be in a position to do much of consequence to or for Britain. The most direct interaction I'd see between Moscow and Red London would be if the Soviets decided to try and do some sort of moral meta-intervention in India, offering the comrades of that subcontinent their guidance and leadership. Since India's anticolonial rebels were mostly not Communists and their point is independence, I don't see that going anywhere much.
When the dust settles in Britain, I'd think the Soviet Union would be a natural ally of Red Britain, and if there is a global Labour Commonwealth, of that entitity too.
The upshot might be very good for both sides, the English-speaking and the Russian, of this meta-alliance. The Soviets needed trade partners with advanced industrial goods to invest in them and build up their industries; the old core of a former capitalist Empire, shorn of her Third-world possessions for the most part, will need resources as inputs and markets as outputs, and the Soviets can offer those. More typically I consider Germany in that symbiotic role, but I believe Britain can serve about as well.
Again the question, as for the USA, is how badly does the British example churn up the other capitalist powers? If they all wind up having left-wing revolutions and the leaders of these movements can live up to the Socialist dogma that worker's states will cooperate rationally with each other, then essentially we've just had Marx's Big Revolution and the workers won. It's not "Red Britain" then, it's a Red World.
So I suppose that here, France and Germany will somehow not be drawn into the vortex, Italy will become and remain Fascist, Japan won't go left and probably the USA and hence Canada remain right-wing. Perhaps the Labour Commonwealth winds up being home to a bunch of American refugees from severe right-wing repression in the name of White Supremacy and "decency."
Well, that's the sort of place I expect to see this wind up; I have no clue how you are going to get us there, or anywhere else you think it would really go.
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