I have just confirmed this and it totally works, buy digital games or digital currency codes from Amazon.com. No shipping required, you get the item you want right away. And almost immediately you'll get an email with a link help you redeeming the promotional items for FF14.

I just purchased Resident Evil REHD and xbox live gold 12 month in total of 55USD, and worked without a hitch.

WARNING!! You DON'T need to purchase more than 25USD worth of stuff, the promotional code provided by Amazon will have a code for EVERY item in the promotion, and they are account wide.

Hope this helps for anyone living outside of US and have NA Region accounts for FF14 and console/steam.