Canada's main attraction is the social services and basicaly guaranteed citizenship. The US's main attraction is money and technical opportunities and also some vague promise of a green card.
If you were not born in China or India, then getting a green card isn't a vague promise. Go work at google, try to get an H1B or L1 ASAP and then get your green card in 1-2 years after that.
Given that much more Chinese and Indians still prefer US to Canada, further and further elongating the lines for green card, it seems the Canadian advantage is not so enticing after all.