I am frequently flying from Brazil to US-I am Brazilian citizen –and so far I was never required on having a visa for US but lately I am about to provided even when I am just passing by US-usually I am flying to Europe and frequently I have indirect flights involving my several hours stay at some US international airport and now I have heard something on possible visa restrictions on Brazil.
Well so far no visa restrictions were obliged but since recently this process involves certain visa restrictions for most of the countries from South America involving Brazil also. Anyway these are just sort of steps of precautions as form of the fight against of possible terrorism attacks I guess and there is nothing else special to it.