If DL starts 330 service to GRU, it likely will be on the new 333s which have higher thrust engines and a higher take off weight. To my knowledge, DL has never brought any of the PMNW 330s (332 or 333) to GRU.
As to the notion that DL has a structural disadvantage, feel free to define it however you would like.
The evidence shows that DL is doing better in maintaining its position in Latin America and generating revenues than other carriers are.
If size is the definition of a structural advantage, then AA has it over EVERY other carrier to Brazil.
But by that token, there are scores of markets where other carriers have a structural advantage over others.
If the issue is serving a particularly gateway over others, then there are equally as many cases where one carrier has it over another.
Plz define "structural advantage" and "structural disadvantage" and don't be surprised if your own definitions are used elsewhere exactly the way you want to use them regarding Brazil service.
meanwhile, DL is adding a 4th gateway and coming closer to competing with MIA and offering better US coverage than not only DL ever has but also better than UA.