I'm really sorry about that!
The key is a leftover from the recent Awesome Indies from Humble Games and there were no reports of region restrictions. I checked. What a pain.
If it's any consolation the few Argentinian born folks I know are fantastic people...

I opened a support ticket for a reroll, but I was told this is not option in this case because a new winner might hit the same problem. And since I don't have a way to provide you with a key that would work at your end (since my key is not supposed to be region locked), I need to ask your permission to delete the giveaway.

Please reply here and let me know if I have your permission to delete the giveaway.

Also, I'd like to report this in the bundle discussion thread, so I'd appreciate it if you can let me know the exact error you get when trying to activate the game.

Again, I'm very sorry about this.
Thanks.

Please try to activate the key, you may not be able to purchase it on steam, but you should be able to activate it.
See the comments here:
https://www.steamgifts.com/go/comment/4loqNuK
Please let me know if this worked out.

Cool! Enjoy!