Canada was really good at making nukes, and there were several times through history that we owned lots of different kinds of nuclear warheads. Although, most were held by US Air Force. Canada was the leader of nuclear tech regarding weapons after WW2. It was the canadian army that controlled a pile of Honest John Nukes in Germany in the late 60s aswell.
I think without canada, the USA would not be the nuclear superpower it is today.
Canada was also were the entire worlds supply of "heavy water" was dealt with.
Canada also stations american nukes until the mid 80s under a dual key policy, were both countries had to agree to press the red button.