Radios are not country locked, to my knowledge. I assume that SiriusXM Canada just inputs the Radio ID in and says, "Oh, there you go." In the 10 years I've been dealing with this, I've never heard of any radio being USA or Canada specific so I'd lean towards: no problems.
With regards to an outdoor Sirius antenna.. Depends. It may work. I've experienced iffy results on mixing Sirius and XM antennas with the other brand's radios in the past. They do have Sirius/XM antennas that are supposed to work on both now, without an issue and some people have gotten some antennas to operate fine with either radio.
I'd say try it and see. If it doesn't work, look into a Pixel (I think it's Pixel 600) antenna. I believe it says it'll work with either and it's a rugged outdoor antenna.