Who knows. But knowing all those bigger cities/states in the U.S, people go there for their jobs. That's why you guys are so populated. There's not any major places in Canada for jobs or anything cool.
Like example: Toronto vs Las Vegas or N.Y.C.
Who the hell would wanna live in Toronto when they could live in N.Y.C or Las Vegas.
The climate could be a factor, but it depends on the person. Myself, I hate the climate here. It's TERRIBLE.