One World Order: Averted. Most species have more than one government. Even the Empire, huge as it is and prone to casual memetic imperialism and absorption as it also is, has spawned splinters – not just the individual Renunciates and Renegades, but some actual other eldraeic governances created by minority factions that just couldn’t get along with the overall libertist-technepraxic consensus. (Given the predicates of said consensus, Imperial relations with these are usually, albeit not always, remarkably toxic – with the splinters being seen as something between heretics and just plain old bastard-coated bastards with bastard-flavored filling.)
Many governments also include more than one species. Looked at either way, no-one speaks for all.
Also, even the supposedly all-encompassing Associated Worlds and Conclave of Galactic Polities don’t encompass everything. The Voniensa Republic prefers to stand aloof from the whole situation, smug gits that they are, and horrified by the sheer lack of control of the whole thing. There are plenty of still balkanized planets around, whether the countries have come together to create some international body to deal with offworld affairs or are each trying to conduct their own interstellar policy. And, heck, encouraged by the fact that at least two of the major powers in the setting are functioning libertarianesque polities that shamelessly encourage this sort of thing, there are a lot of independent habitats out there that have taken advantage of the vastness of space to declare themselves the Sovereign Polity of Brad & Janet, pop. 5, or just straight-out sovereign not-owned-by-any-government individuals, m’kay?
Unity is not where it is at, today.