I think the stories of CE having taken over the entire island are just a tad exaggerated.
Well, jaune is the only one saying that, and he is obviously biased. If you are getting beaten, you would want to describe your opponent as some unstoppable monster, so that you don't come off looking too bad for losing.
CE might be the strongest realm on AT (debatable), but she is far from hegemony. Being able to defend herself is a very different thing from being able to subjugate the entire island.