While you're broadly right, I should say that it's difficult to figure out how far 'Amaurot' goes. And by 'Amaurot' I mean the civilization that the city was a capital of, for clarification. All evidence does seem to suggest that the species we know of as the 'Ancients'--thirty feet tall, effectively immortal, creation magic--were the dominant species across the planet, because everything seems to suggest that there weren't meaningful differences--and the Ancient's overall self-image of superiority can be evidence of that, because they probably would've spoken of 'lesser people' had those people existed.
It's very hard to tell if the nation of Amaurot was a one-world government, or just the only one we heard about--basically, 'one relevant world government'. We do hear about other, smaller settlements in both the Azem and Venat short stories, as well as the places that already fell to the End of Days as of the Fake Amaurot snapshot, but there's never enough context to tell if they're another civilization entirely or if it's just a fair distance away. In real-world terms (because I think they're extremely useful metaphors to understand and contextualize this stuff, for people who wonder why I do throw those down), if Amaurot is modern Washington DC, we don't know if the volcano island Azem saved was Hawaii or New Zealand.
But what we DO know is that when the End of Days finally hit the city of Amaurot's shores, they decreed 'let's sacrifice half the planet to create a god'. That suggests one of three things:
- That Amaurot genuinely was the major governing seat of the world,
- that at that point there wasn't much left so they assumed control over what was, or
- that there were other governments and societies around, but Amaurot doesn't care about their autonomy.
All three of those suggest the city of Amaurot had VERY big heads, although possibility 2 I could at least swallow if it were put to me in an actual story.
The underlining point of the Amaurot story has always been 'hubris', though, and we really shouldn't forget or neglect that. Amaurot was full of people making understandable human mistakes with dire consequences.