Sure. The cultures amenable to joining the Federation were not particularly strong in the first place. If they were, they'd have built an empire of their own. Therefore the cultures that did build empires are capable of standing up to a Federation of mostly peaceful peoples. The fact that mostly humans are seen in Starfleet, and that Starfleet is originally an Earth institution suggests that humans are the primary defenders of the Federation. In a way, humans built an empire out of cooperating with weaker species, instead of conquering them like Klingons or Romulans do. Cardassians managed to be more devious about their empire-building, by insinuating themselves into the Bajoran culture. So the Federation is just the Human Empire by another name, and better at empire building than their competitors.
Basically, the Federation isn't as much more powerful than the surrounding empires as it may seem, they're just less obvious about being an empire. Which I think explains the political situation nicely.