XCom is 2K and I think last I heard they were store locking in Nuuvem but not necessarily region locking once you get the key to activate on Steam. Meaning you'd either have to use a VPN to buy it or else get someone in South America to buy it for you.
Since it's a pre-release there's also always the possibility the publisher could add an 11th hour Brazil or South America specific region lock to the Steam database. That happened with Saints Row IV.
I'd say it's probably not a good idea to pre-order AAA stuff but anything indie you should be fine and anything AAA already released if you just through hoops to get the key from the store and get a key now it will probably be okay, but depends on the publisher. Definitely don't buy anything from Deep Silver or Sega there because those are for sure region locked in the Steam db.
You can always try and check the steam database yourself at
https://steamdb.info/
If you look up the game (make sure it's the actual game and not the DLC), check the packages tab on the left and see something like this:
then it's region locked so don't buy it. You want to look out for "BR" or "SA" which stand for Brazil and South America respectively. Those won't activate onto Steam outside those regions (unless you use a vpn and uh, just don't. It's one thing to use it on a store but another to use it on Steam where you've likely invested a lot of money in your account).
There's also a rare NCSA region lock that stands for North, Central and South America, but if you're in the US or Canada you're fine on that one.
ing Chatwin.
