Originally Posted by
ty97
Definitely need to check the visa rules, though my understanding (but OP should verify!) is that you can transit GRU without a visa if your final destination is outside Brazil.
Before I posted above I did a quick Google Flights search for Delta flight to MVD on a random date. I was surprised that only GRU connections to GOL came up and I didn't see any connection options through EZE which I would have expected to exist.
I think the OP should start by calling DL to ask about connections through EZE (or EZE and AEP), GRU, and GIG. DL agents might be able to book partner flights on the same ticket even if they're not codeshare and don't show up when one searches.
Within Brazil, there are a lot of GOL flights that go via some third airport, including GRU-GIG-XXX or GIG-GRU-XXX, and thus require lots of extra time. These would seem to definitely require a visa, at a cost of about $160 plus visa service fees as the Brazilian consulates do not accept visa applications that are not delivered and fetched by a person rather than mail or FedEx.
AFAIK Argentina currently still has not reinstated the reciprocity fee, which had been about $160 paid in advance on the website and usually approved instantly. Check the Argentina destination forum for details and current information on this. Also, AFAIK the Brazilian visa waiver for the Olympics has ended and has not been extended, although there's some talk of visa requirements for USA passports perhaps being dropped in the future.