Yeah me too. After some confusion from various posters, I'd thought I'd waste 15 minutes trying to see if I could get it myself (UK resident, EU realm), short answer is NO.
"This item can only be delivered to a US World of Warcraft account."

You don't have to register with the mountain dew website for the promotion and you CAN log in directly to your EU Battle.net account from a US Battle.net account login screen (which the redemption screen directs you too). However you will ultimately be greeted with the above message.

Note, in theory you could be a resident outside the US and claim this promotion, as long as you have a US WoW account.

Lol, its possible, just click on the link from the mountendew site and login with your battle.net account (http://www.mountaindewgamefuel.com/redeem.php).

Got the pet on european server xD, the text in the letter is translated and everything!

And too "This item can only be delivered to a US World of Warcraft account.".

Got the message too, but i clicked on the button below and the pet was send to all chars.

Maybe it has something to do with the battle.net site translation? I used the german one.

IT IS possible to get the pet, you just have to ignore the 'This is for US only' after you log in through the US Battle.net site and just click redeem (make sure you are on the WoW Client Log in screen before you click it).

Thanks Hikaru (and others).
I now have my pet. I was getting persistent "Redemption Error" and "Page Not Found" errors after clicking the 'Redeem' button, I assumed this was location related, but in hindsight it's probably just a server-load issue.
So with persistence, on my fifth try, I finally got "Redemption Successful". Checked my account and I have my new pet.
Cheers.
Ehm so sorry for the confusion (whoops!) EU Players CAN get this pet.

Visit the same link each day to redeem new cases (5x bottles) of fuel, in red or blue.

Well, it seems it's no longer possible now. At least not for some players. It didn't work for me, and after reading a little in the forumpost posted later in this thread it seems that
A) either it was bug on the part of the mountaindew/battle.net sites, or
B) like some guy said: he spoke to a GM and the GM told him that yes, it was possible to get the pet on a EU account, but there was a bug ingame with that now which they were fixing.

I am REALLY hoping for B.
I've made a ticket in the hope of finding out more.

(And I also heard there is a Spanish guy actually suing Blizzard for this, wow, lol?)

I HATE globe of USofA!!!