^There's no indication that there wasn't a Romulan schism in ST XI either. It's not like Nero would've stopped to give a dissertation on recent politics while accusing Spock of murdering his homeworld. As for Countdown, where's the evidence there? Even with the Imperial Romulan State having broken off, there's still a government called the Romulan Star Empire whose capital is on Romulus. And I doubt anyone in Countdown said, "Well, considering that no rival empire has broken away from the Romulan Star Empire in the past decade...." By the same token, just because a few novels have featured a few Romulan colonies that are sparsely populated, there's no logical basis for assuming that more heavily populated planets don't exist elsewhere in the empire. Absence of evidence is not evidence of absence. If you only knew about the 19th-century United States from Westerns set in small towns and farming communities, would you conclude that there was no such place as New York City or Chicago or Philadelphia?
I know all that, Christopher. I was just stating the impressions I got watching the film and reading the comics and books, and my fan theroies. I don't presume to think of my opinions as stone-cold truth. Even if the film had said something to strongly imply that there wasn't a rival Romulan faction in 2387, it's not as though the novels couldn't find a way around that if they really wanted to.
There was a very important scene set in a city on a Romulan planet that established that there was a huge humanitarian crisis on the Star Empire. We don't get a sense of how many Romulans live off-Romulus, but it was clear that the population is big.