Looking at Canada with Google Earth, I've noticed how large are the states (I don't know if that is the right denomination - maybe provinces?) when compared to the USA states - from 2-3 times larger that most of them, and how few they are,

Ontario and Quebec have the size of whole countries!

Why is that? Due to climate (at the extreme north there are the Northwest Territories, the Yukon Territories and Nunavut, that seemed to me to be as desolated as Alaska)? Population distribution? Ethnics?