Is this for USA only, or can I use it in Canada?
Monbux, great question, unfortunately I do not know.
I normally use scriptsmart to check out gift card ratings and find out the terms of use for the card, I linked you to the review below.
It does not say one way or the other, your best bet would be to call staples and ask them.
http://www.scripsmart.com/giftcards/791-staples-egift-card