I disagree. It looked much more like the US was playing without the midfield. When you consider that Marta was an attacking mid for brazil, and as such should have been Boxx's mark, and when you consider that Foudy, Lilly, and Wagner barely touched the ball the first half, I'd have to say Brazil's midfield was frighteningly effective.
Brazil was frightenly effective in the first half everywhere, period. I too think its too simple to say the midfield adjustment was the only reason we looked better the second half. Brazil was not the same team that half, and I would attribute that to fatigue/fitness. We were damn lucky they backed off a bit.