In this trailer Cersei Lannister says:
My only venture at this moment is establishing control over this continent and every person on it.
I'm not sure, but by using this instead of the, they just implied that Westeros is one of many continents, and that everybody knows that as a fact. By everybody I mean at least those that Cersei is talking to.
There is been a while since I listened to the audiobooks, so don't quote me on this one, but I don't recall the author ever acknowledging the existence of more continents beside Westeros. Thus my question, was it ever acknowledged or hinted in the books that Westeros was one of many continents?