does NAFTA benefit Canada?

recently both Obama and Clinton have both stated that they will renegotiate or pull out of NAFTA. seeing as NAFTA has never been truly followed AND Canada continues to be taxed and are continued to be subject to tariffs while the sates are able to continue on this path without punishment.

if it will happen or not could pulling of of NAFTA or renegotiating it (provided the Canadian government stands up for the Canadian people and doesn't back down like a whimpering dog) benefit Canada?