I mean having 100 different countries on a planet, each with space age technology, there would be a problem. There just wouldn’t be enough real estate for that many countries to stake claims and progress forward. On the other hand if there was only a few, say 2-4, countries with space age technology it might work.
I see it going as not having to unify to progress onward, but giving a detriment (based on how many other countries with space age technology there are) to players if they decide to not unify.
I don’t necessarily see it as a problem in the early space stage. But the internal conflicts could really make it difficult for you to progress to a galactic empire stage. Though I suppose even then the different factions from your starting planet could claim their own solar systems, so you could keep playing against them and competing. But maybe there could be some harsh penalties to encourage players to unite their planets. For example your rival factions could get a huge boost for researching tech you have, so it would be way more difficult than normal to ascend first.
The improvements in technology may make continuing to have a large empire easy (the far away provinces not rebelling) and small states may be gobbled up by a few large ones. The improvements in mass media and things like the schengen area may make different cultures assimilate each other. The borders of old may end up being a mere formality and eventually be scrapped altogether. Alternatively the game may not simulate small states outside of their planets (like island nations in the Pacific which only influence UN resolutions)
The species may unite, and then fracture again. This is what happened in All Tomorrows between those who remained on Earth and those who colonised Mars (and what will happen to us if Elon Musk’s proposals are accepted). Different political formations of the same species may exist exactly like that of different species or the same species may have a positive relations affect on each other (+25 you are our kinsmen)