It should also be noted that Brazillian anti-american trends are of the soft kind, like the European version. Basicly, a lot of people may have opinions that put them under this label, but it is only a matter of opinions on history and someone elses foreign policy or society expressed in a manner that is strictly superficial and produces no direct results.
This type of "do they hate us" polls need to be taken with carefull consideration. If you ask the Bush aproval ratings back in the day, with a yes or no question, a laid-back, perfectly peacefull and well-meaning university student with no strong political beliefs would say no, and so would a die-hard fanatic targeting US soldiers, yet they are very diferent things. Going by this one would end up thinking the hatred of the US is far more intense is peacefull Brazil than North Korea or Iran.
I honestly believe this kind of "anti-americanism" is the stricly superficial, social one, the kind that does not affect business or security. The political stance is also more along the lines of stressing out Brazil will act internationally in an independent way, and showing the US they see themselves as players and do not expect to be dealt with by pressure. In short, it may make them politically unreliable, but I don't see any kind of economical or political warfare coming from there.