Cat
There are a few different ways you can register on the USA sight.
I have done both successfully.
1. You can buy a USA iTunes gift card off ebay from someone selling them....they usually charge $120.00 for a $100 card. Then use any USA address when creating your account and instead of a credit card, redeem the gift card.
2. You can buy pre-paid Matercards from shoppers drug marts in Canada. They are called Vanilla Mastercards ( and shoppers will have lots).
After you buy it, go to the web site and register it...again use any USA address..then use the same address when signing up to the USA iTunes store...put in the master card number and expiration date etc..and you will then have a USA account. Once your card runs out, buy another...register it under same address, then go to your iTunes account and just change the credit card number to the new one.
J