What did you put as a postal code? I used a US postal code and US state with my Canadian Mastercard. Though I used my Canadian street address and phone number - I don't think they matter.
I saw your post where you said you got the Google Music All Access to work...Just curious how you did that. I'm in Vancouver, trying to sign up, and when I get to the checkout it tells me that my VISA is an Unsupported Payment Method.