I'll dispute that. In my experience, Brazil is a better melting pot.
Anecdotal example: In Brazil, you don't see people claiming they are Irish when their families have lived in the US for generations.
That is actually the key to Americas success. The total separation of ethnicity and national identity. It allows an immigrant to keep their ethnic identity and merely add an American one.
It's also helps when a white 5th generation american thinks they are Irish and American. They'll be less likely to believe that a newly arrived Mexican isn't really American. They intuitively know you can be both.
America's success results largely from its geography. Being isolated from Europe by a large ocean and having the mighty Mississippi river system to build an agricultural powerhouse from made it pretty much inevitable.
In Brazil, you're just Brazilian, regardless of color.
Also, as if by magic, 100% of them appear white (or mostly white), despite non-whites making up a large fraction of Brazil's population.
It's absurd to act like everything is great for racial minorities in Brazil.
http://www.vice.com/read/welcome-to-americana-brazil-0000580...
But I agree that Brazil overall is an impressive melting pot, on par or better than the US.