That's actually a pretty good question, and one I don't think anyone really knows the proper answer to. She's been "Princess" for so long that we all just go with it, I don't think we've ever had a real Queen. I do have a theory, based on semi-recent evidence, but it's not much more than a wild guess.

Fascinating. Fifty states, each at the very least over a thousand five hundred square miles across... There must be a lot of humans just to take up that much space.

Honestly, I'm not entirely sure. I don't think the whole world's ever been explored yet, primarily because while Equestria itself is a veritable paradise, things beyond our borders tend to get... dangerous. Just as an example, hiking through a mountain range is one thing.

Hiking through a mountain range inhabited by dragons is another matter entirely.

I am aware of four nations. Equestria, the Gryphon Kingdom, the Zebra lands, which may or may not be divided up into smaller nations, the only zebra I know doesn't talk about it all that much, and the Buffalo tribes, who I count as a nation because they have a unique culture, though they're largely nomadic and it would be hard to put their territory on a map.