According to our Terms and Conditions, our gift cards can be redeemed in the local currency by domiciled residents of that country. Therefore, it is not allowed to transact in a currency other than your local one i.e. it is not possible to have a USD gift card and transact in CAD. You will be able to see the settings of the currency on the website on the top of the page.
Please note that you can see the currency of your gift card once you receive it.