It has been some decades

since I read the book, but I did like it a lot when I read it.
I don't remember any "dystopic" future being clearly indicated; the last paragraph (if I recall correctly) might suggest that, or it could just be a glimpse at a weird future with its terrors but also beauties, as seems likely if you start the clock of exponential growth of computing power way back in the middle of the 19th century!
As for "butterflies," I take the position that if we want a timeline with some dramatic POD way back in time but we still want parallelism, we can have it without worrying about
random/chaotic butterflies of the "different sperm meets egg" variety--insofar, that is, as these "butterflies" are due to mere randomness. We can bear in mind that if there are numerous timelines stemming from PODs from our exact past, meanwhile there were at the time of any given POD, other timelines already in existence from earlier PODs, some of which will, due precisely to these same "butterflies" operating on it, appear to closely parallel OTL at that moment to all macro-scale evidence. We could have our POD happen in one of those, and the different butterflies working on different (but only microscopically and unobservably so) initial conditions will, among the infinite timelines emerging from that POD, include ones that happen to parallel OTL--we can look at one of those and call it our alt-timeline.
Well and good, for
random butterflies. But what we are looking at in an interesting alternate timeline is new, significant alternative historical events that have
systematic consequences, and these will tend increasingly to
systematically preclude parallelism of people and institutions and cities and so forth.
In
The Difference Engine for instance, the United States is Balkanized, with a Confederacy, an independent Texas and California republic, IIRC Deseret, and the Manhattan Commune under Karl Marx's leadership all split off from the USA--there might even have been a New England confederacy as well. Obviously the marriages of the Roosevelt family are going to be affected! Well, if the Roosevelts, being New York Patroons, choose to marry within their narrow and local circle as I suspect they did OTL, we can invoke the above-mentioned "Anti-Butterflies" (ie, we choose a timeline where the butterflies happen to produce the same result as OTL in purely chaotic matters) to still get Theodore if we want him. But if in fact OTL Theodore's ancestors included people it would be implausible to have getting married in the late 19th century in this timeline, then he's gone--not so much "butterflied" as eliminated by the logic of the timeline.
The reason the USA is shattered, it is pretty much stated clearly IIRC, is that the British Rad Lords have been enacting a policy of weakening their potential American rival with dramatic results.
So I suspect the Manhattan Commune is in some peril; it may have been convenient for British interests to have the USA's main and growing port city split off, even under a radical Communist, and perhaps Marx's theory of Communism seems less incisive and threatening in this timeline, given the pragmatic empirical progressivism of the Radical Lords of the Byron/Babbage tradition. Still I suspect sooner or later the British will seek to swat the annoying fly of incitement to proletarian revolution.
This might backfire on them, maybe Marx's Commune will be the seed of a new Communist version of the USA; perhaps a Marxist framework is just what the Americans need to catch up and overtake the Rad Lord's Machine-aided computational Machiavellian order.
Marx of course was not much of a leader of organized movements; he was widely revered as a prophet and visionary, but when he tried to lead actual organizations, he had his core of loyalists but also badly alienated others, leading to major factional splits. As I rather like Marx and the idea of a Manhattan Commune (and perhaps greater Communal Union of North America?) I rather hope he's survived in power thus far because among his loyalists are some lieutenants who manage the interpersonal politics for him.
All this stuff about Marx is by way of getting to answering someone else's question about Lenin:
It seems likely to me that
systematic changes to Russia will make the appearance of Lenin or any other members of the Bolshevik cast unlikely. However Russian society by its size and isolation from Western Europe may indeed insulate the affairs of the kind of people who were ancestors of Lenin, Trotsky, Stalin, et al so that our "antibutterfly" solution may apply and we have these very people. And the situation of Russia, while systematically different, may be quite similar--too backward to win against Western Europe but too big to be subdued by them, too useful in its reactionary potentials for Western powers to systematically want to see its regime destroyed but having too much economic potential for them to leave the place alone either. Upshot, massive discontent and a search for a viable and if at all possible distinctively "Russian" solution. If the Manhattan Commune is still there, or has even grown, it might be the inspiration of some of these factions of Russian dissidents (vice versa though its very success might give it less of a mythic cachet than the world's Leftists of the late 19th/early 20th century got from the romantic martyrdom of the Paris Commune and other abortive revolutions--so maybe if you want alt-Lenin, you need for the Manhattan Commune to be brutally surpressed


).
If the "dystopic" end of the novel is indeed the triumph of a transhuman Machine society in which humanity is irrelevant, it still will take a long time to get there. Difference Engine type computers are inherently very slow compared to electronic ones. Presumably electronics will get developed earlier than OTL and then the rate will pick up, presumably developing transistors, integrated then printed circuits, etc. But this will still take time!
Lots of time, generations then, to write timelines about essentially human steampunk societies that may or may not succumb to the Robot Revolt.