Well, both the northern Native Americans and the Maya/Aztecs were decentralized, and the Maya had developed these conquest rituals between their city-states that actually cost them very few men (they only attacked another city-state at certain times, and if they captured the king they won; it was almost a game), but of course the Europeans did not play by those rules, and neither American culture was the aggressor.
On Kulthea we have Sel-kai, the Renaissance Venice of the Shadow World, which extends its trade influence, and the rich merchants are happy with their islands, and the Namarian Elves have their own protected island cluster, and they have a small, fairly static population. Namar-Tol is more like the US pre WWII... they really want to just stay out of it, but if the Lankani are stupid enough to attack them, they will punish them. But Lankanok is big, has psycho leaders with a god complex, and has a large population of religiously driven pawns to spend...
And while Earth has oceans, the Shadow World has ever-changing Essænce Barriers (which I think I have not emphasized enough in later books).
The Alliance is much more like the invading Spaniards than anyone else.
Just more thoughts off the top of my head to ponder, loving the discussion.