Just to follow up on my earlier comments, I would say quite categorically that the alliance BMD is not so much directed towards Russia as it is directed towards Iran and other emerging nuclear states. The NATO umbrella will never be capable of tackling the sorts of capabilities that the Russians have, at least not for decades to come.
One has to ask whether Canada is really threatened by Iran. Is Canada really threatened by North Korea? If the answer, particularly to that second question, is yes, then you need to start thinking about whether missile defence contributes to your protection.