It seems that it is common that the baggage allowance on flights to Brazil is more generous (both in number of pieces and weight) than to other countries. In fact many airlines, have a specific exception to their general rules for Brazil. Examples:
I've heard a rumor, that this may be related to international treaties, but I'm not sure. Does anyone know the answer?
Related question: Why is TAM Airlines baggage allowance so much? [closed]