South American countries only have a limited version of the eShop available where you have to purchase codes on a separate website and then redeem them on your Switch. That's the 16-digit-code you get asked to enter.
It's possible for anyone to change the country on their console and access other versions of the eShop, so I assume that most South Americans use the USA version where all content can be browsed freely. You can try ask someone like mzuzek via PM how exactly it works, or alternatively use Google to search for quick guides on how to set things up. It's probably easiest to create a new account on the Switch console and use that one for purchases; the other accounts should be able to access all purchased content without problems.
Thank you, the FAQ I checked didn't had it. Great help, perhaps I'll attach an account with USA.
duduspace11 "Well, since we are estimating costs, Pokemon Red/Blue did cost Nintendo about $50m to make back in 1996"
Mr Puggsly: "Hehe, I said good profit. You said big profit. Frankly, not losing money is what I meant by good. Don't get hung up on semantics"
Azzanation: "PS5 wouldn't sold out at launch without scalpers."