Considering that the strong Canadian dollar is really hurting Canadian manufacturing right now, I'm surprised Canada isn't trying to renegotiate NAFTA.
My guess is that Harper is just getting tired of the US Democrats ignoring the facts and complaining that NAFTA is harming the US because it's a favorite bogeyman of organized labor.
If you think we have it bad, due to the change in the value of the dollar the cost of producing goods in Canada for the US market jumped 30% in the last year. Ontario's auto industry is really hurting right now.
The only reason Ford, GM, etc moved production to Canada was the health Ins savings.