The score is 320,000,000 or so to 36,000,000....the immigration south versus north is usually anywhere from 4 to 1 to 6 or 8 to 1...

Even that most Canadian of stereotypes -the hockey player usually retires in the USA. Our two, three greatest living - Orr, Gretzky and Lemieux all live in the USA 

American athletes coming north? Football? Baseball? Even hockey? How many stay?

And since both countries are immigrant based it is not like comparisons to India or china...

Don't get me wrong, Canada is a great country, but the USA has many more opportunities for a wider range of people