In January 2015, Citizenship and Immigration Canada (CIC) will launch a new electronic system called Express Entry to manage applications for permanent residence in certain economic programs. Canada needs high levels of immigration to meet current and future labour market needs, which will ensure our economic growth and long-term prosperity.

http://www.cic.gc.ca/english/immigrate/express/express-entry.asp

Key sentence: "Canada needs high levels of immigration."
Answer is Motivation. Sure, US needs more skilled labors, but it faces harsh criticism for a liberal immigration policy as well. Hence there always will be a very slow progress if any.

That is because Canadian immigration is based on labor market and America prefers more Family based immigration.