He can re-gift it to someone else who is using the Mexico iTunes store. He needs to sign into his iTunes account, and go to his Account Information page. Under Purchase History he will see a section called Gifts with an option to click on Manage Gifts.
He will see a list of gifts he has sent. If he clicks on the one he sent to you, since you have not redeemed it, it will show a box with the recipient name on it, and will let him change it to any other email address he wishes to:
The reason you cannot send gifts to recipients using other iTunes stores, is because the item sent may or may not exist in your store. Also, there are restrictions for content in many countries.
Sorry 😟,
GB