I'm sure you can do that!
I'm in Sweden and my HD/HD+ is from USA. It works just like any other Google enabled device. I get all my apps from Google Play Store and my books frpm the local library.
Pretty sure you need to register a usa residential address when you set up your Barnes and Noble account to access US books and apps. My Nook is registered to uk residential address and I am limited to Uk content. So whatever Google apps are available in Brazil should be accessible with a Brazilian address on your account. Not sure if B&N store covers Brazil........ worth checking before you buy. You should be able to download from free sites like Project Guttenberg ok
To buy BN books and apps you need to register a US/UK address and a US/UK credit card address and posssibly also go through a VPN. I don't know because I have never felt the need for any of this.
To just register the device you don't have to give any address info at all. Just an e-mail (and the system doesn't even check that)
Ok - I know that the systems work a bit differently in UK/USA.
When I signed up for a B&N account, which I needed to sign into my Nook HD+ to set it up, I had to put down a residence address & country, not just my email address.
I remember you saying on a previous thread, Swedereades, that you do have a US address even though you don't live there - not sure if you used that when you set up your B&N account....