Thank you for reporting this, Salonaut .
The fact that you see this Russian locked product in USA is an error on our part. We don't normally include region locked keys on a game page. Instead we match RU products to the Russian region, US products to USA and so on. Somehow this particular product has managed to bypass our region matching rules.
We will correct this mistake and figure out why this problem occured in first place to make sure it doesn't happen again.