I wouldn't complete count out USA against Brazil if they should meet. Brazil has not looked very impressive so far -- if the US can find someone to actually finish a chance or two, they can score. The real challenge will be preventing the Brazilian counter-attack. On the whole, I think the same style and strategy used against Italy would serve Team USA well against Brazil -- high-tempo, agressive, break up the rhythm.
We did ok against Brazil in 94, I even think we had a one man advantage against Brazil, but Brazil still won 1-0. But at least we were competitive in that game.
Also if the US does better than Mexico, that is also success for the US. Mexico still may not make it out of their group.