Cannot switch App Store Region/Country with active Apple subscription

Jeff, thank you for your reply.

Yes, I am aware that I can access through American Express Canada web site, however, I was hoping to retain the convenience factor.  I find it frustrating that two multinational companies cannot maintain ease of access for their customers.

Went to the Apple store and spoke to the store Manager. She suggested that we purchase another iWatch 10 online at the store and that would allow us to add/purchase a 2-year warranty online without annual subscription. Upon delivery of the new watch ordered online at the store, we returned the 1-week old iWatch 10. Seems inefficient and added work for everyone involved but it worked. She said that the subcription only warranty through purchases at the store (versus online) had only been in effect for the last couple of weeks and that most in store purchasers preferred the annual subscription warranty over adding the 2-year warranty purchase at the time of the device purchase, maybe to reduce initial cost outlay? She thought this was the rationale for forcing the annual warranty subscription option when purchasing directly from an Apple store.

I have successfully been able to switch back to the Canadian app store to refresh my mobile Canadian Amex app and then return back to the U.S. app store. Thanks for your help.