The world is changing, we need to change as well. What if Canada deals with USA in such a way. It promises to invest more money in defence while buying more equipments from USA. Also it invests more money in defence related R&D in collaboration with US to develop indigenous technologies  especially needed in NORAD. In general also if Canada ramps up its defence budget and spends on it buying from the US. This way we both achieve trade balance. At the same time our country also advances in terms of our military and defence systems. Also if our country men and women can work more and earn more and compensate to such spendings while our countries GDP goes up. No use of loosing money in tariffs instead use our money wisely and for our countries benefit.