To properly analyse how having a different Earth would affect TiTS, we'll need to compare the faction that rules that Earth to the Terran Space Coalition. I'm not familiar enough with Star Trek to do any speculating on that part, so I'll go to my default fallback instead: Mass Effect. In this case, that means the Systems Alliance.
One of the most important differences between the Systems Alliance and the Terran Space Coalition is how they were formed; while both of them formed from the United Nations after discovering that aliens exist, the context behind that discovery is very different between the two. For the Alliance, the discovery was of Prothean ruins on Mars, before humanity had even left the Sol system; for the TSC, it was First Contact with an ausar colony, after many human colonies had already been founded and declared independence from Earth.
As a result of this, the vast majority of human colonies in ME were founded under the Alliance's banner, while early human colonies in TiTS often enjoyed decades if not centuries of independence prior to the TSC's formation, and some (like Vesperia and New Texas) remained independent even after being connected to the Warp Gate network. As such, the Alliance's member worlds are much more unified than those of the TSC; since the TSC's lack of unity is likely a contributing factor to humanity's lack of influence on the galactic scale in TiTS, the Alliance transplanted into TiTS would thus cause humanity to wield significantly more influence, probably on par with the JAF. This unified presence would have further ramifications:
- Due to ethical oversight, New Texas would not have been able to develop the Treatment and would likely be an unremarkable agricultural world.
- The presence of the Nova on Tarkus would pique the Alliance's interest, and they'd send official teams to investigate. Since it's implied Victor sent Anno there at least in part to do that, there's a chance she and Steele would never be able to meet outside Puppyslutmas.
- It provides less room for megacorps to gain power within Alliance territory; this doesn't prevent them from popping up, it just means they'll likely be less powerful.
Another important difference is the Sudham-Wolcott Genetic Heritage Act, which arose out of concerns about losing Earth's unique biodiversity and imposes sharp restrictions on controversial uses of genetic modification. The two most important pieces of this Act are:
ME Codex: Genetic Engineering said:
ENHANCEMENT: Improvement of natural human abilities is legal, but adding new abilities is not. Treatments to improve strength, reflexes, mental ability, or appearance are permitted; adding a tail or the ability to digest cellulose is not.
...
ENGINEERING: Artificial hybridization of genes from compatible non-human species with human genetic code is illegal. Creation of designed life is broadly legal (and mainly used for terraforming and medical applications), but sentient creatures are heavily regulated, and creation of sapient life is outlawed by both the Systems Alliance and the Citadel Council.
This means that transformative gene mods are completely illegal in Alliance space; Vesperians lacking their traditional tauric appearance is the least of the ramifications of this. Since the Alliance would have been one of the founding members of the UGC, its culture would have a broad impact on that of the UGC as a whole, and between this and the JAF's anti-furry culture, it's entirely likely that transformative gene mods (aside from potentially sex and gender TFs) would also be illegal in the UGC as a whole. On the plus side, this means Xenogen and its less-than-ethical practices wouldn't exist.
On the other hand, the existence of naturally-occurring human-alien hybrids would cause many people to realise that the principles upon which the Act was founded are not as important as they thought, which may lead to the Act's restrictions being loosened or even abolished.
Another thing: if the Prothean ruins on Mars exist, that means the Mass Relays and the Reapers might also exist, which could potentially change the TiTSverse so much as to be unrecognisable.
Incidentally, this also reminds me of a standard Mass Effect fanfic template: "what if it was X other human government instead of the Alliance during the First Contact War?", which I have thought about for the TSC.
