Sending money or giftcards in the mail is just begging to lose the money. Not sure why anyone would gamble on that that when paypal/venmo and online banks and gifting on digital game platforms exists.

If you can't help it and it still happens here or there by accident, I believe you are permitted to give them the code to a US friend and have them gift you games with the funds. Hell, I'd do it for you if you didn't have a friend in mind. There could possibly be an issue with a game being US region locked or only available in canada or something, so I would research how that works beforehand (I think just having them start the gift purchase is enough to see if that game is blocked or not, as it pulls up the friends list).