If we're talking about the defence of North America, the elephant in the room is Mexico and at what point Mexico needs to be included in NORAD. This is something that Canada traditionally has not wanted to have happen, although Mexico does have liaison officers at USNORTHCOM.
But it is something also to keep in mind, because Mexico and Canada are similar, in that we're both geographically located next to this major superpower, so there are things we can learn from each other. I know we tend to discount Mexico right away because we traditionally have not wanted to be associated with them in the defence of North America, but down the road, we may now have to reconsider that.