It wouldn't be that easy. There are NORAD radar installations on the very northern parts of Canada. The US would have to come up with something to replace them and continue to have the same capability from US soil or maybe some sort of space radar that can take the place of NORAD radar installations in Canada.
That can be arranged. I have no doubt that if we decide to have a spaced based radar station we could quickly do it. I would love to see the look on the faces of the liberal Canooks when we tell them that our satallite will stop missiles aimed at the US, but good luck to them at stopping anything aimed at Canada.