Trump is not looking at Canada. His spokespeople had stated that we have the same/close-to labour costs as that of the US so the competitive advantage is minimal. However, team JT jumped the gun after the election and said they are open to re-examining NAFTA. In doing so, the incoming administration pretty much said, "...sure, but we were talking about Mexico but if you want to renegotiate then we'll add you in". 
Good job team JT, you really messed that up and now it's going to cost us. Harper would have held his tongue and waited for Trump to see what their intentions truly were.