US Credit Cards
I'll definitely look into the TD visa adding a US address.
What's worked for me is an account with myus.com which receives mail for you at a mailbox in Florida and will forward mail and packages to a Canadian address for you. The box uses an apartment number instead of a P.O. box number so they can accept courier packages for you.
For credit cards, if you're ever in the US, you can buy a prepaid Visa / Mastercard gift card (for up to $500) at practically any convenience store or supermarket and then add a billing address on the website for the card without any kind of verification.
Voila... 1 US mailing/billing address and 1 US Visa card number.. It's highly impractical for constant purchases but I can download US only iTunes content with no problems.