You won't get your PR card until "after" you have "landed". So if you are IN Canada, you will receive a COPR with which you can "flag-pole" i.e. drive to the U.S. border, get turned around there by telling them you just want to "land" in Canada. BTW, you don't need any U.S. visa for any of that. Once "landed", you will get your PR card after that.
I've made certain assumptions not provided for the above post.