Hello @Miki7as,
Welcome to the community!
You can see the coverage area for Canada here, it also depends on your phone once your phone has all the compatible bands required for the Fido network then you should not have issues. You can find the required bands/frequencies for Fido here.
In terms of coverage in USA, it depends on the roaming partner network there and again once your phone is compatible with the network there you should have any issues.
