This is something that Dynon has considered. The business issue with XM support is that it is not "non-US", it's "parts of Canada." XM doesn't work in Europe, Australia, south america, or anywhere else, and it doesn't even cover all of Canada. If this got us wider coverage it would be a pretty easy thing for us to justify. Given that it is not a trivial thing to implement, it just doesn't make sense right now.
As with almost every feature, we are not saying "never" but we just don't have any plans to do it any time soon, and we want people to be able to make their decisions with that data in mind.