What it says is that the site must be a commercial site and it must also be in English. I think the U.S. only part has to do with the credit card processing. Many U.S. companies will not process non-u.s. credit cards. If your site meets all the other requirements, and you used a U.S. credit card, I think it would get processed like any other submission. I'm a bit of nervy here if everything goes bad.
Canadian cards are ok eh.
Yup - Canadian cards processed fine. Thanks guys aren't you all sleeping yet - well it's life isn't it. The Canadian credit card should not be a problem. That's great Caine, it's always encouraging to hear news like yours regarding Yahoo. It serves to show that being successful with Yahoo is a combination of luck and perseverance.