Not certain what you expected- Brasil's population is very diverse, man. It's not just indigenous people and the descendants of enslaved Africans.
--Reports in the media have said that Viradouro had planned to feature at least one dancer dressed as Adolf Hitler in the parade, using the theme: "It Gives you Goose Bumps."-- It gives me Goose Steps.
I wonder, what would be the response if something like this happened in the US? Under American laws, would it be protected as 'free speech'?
Probably protected, but not likely to happen, at least not at something as big here as Carnival is there. You'd be talking a Macy's parade, and even that wouldn't compare. What makes it less likely to happen here isn't the lack of willingness on the part of those who find humor in the Holocaust to try it. I recall trying to tell people when the Mimin Penguin stamp came out in Mexico that it wasn't that the majority culture here is inherently any better, but that the minority culture here is much larger and more vocal about that sort of thing.