Maybe because Brazil does not trust USA, after the WWII interference (long story, I won't explain now... I explained it in past comments), and what happened in cold war (US backed a military coup, sending aircraft carriers even, to ensure it would happen), and what it still do with our media (the biggest print company for example, has as backer the Ford Foundation, and the company was created when Ford Foundation was a sort of front for the CIA, their magazines still are greatly pro-US, and it is obvious they also help with US espionage)

Or you know, re-creating the south-american navy fleet right after Brazil officially announces it found massive amounts of oil on its coast!

Thus, since US do that, and Brazil does not trust US, Brazil closed ties with Russia and China, that actually help (specially Russia... For example, when US sent its newly reactivated fleet to our shores right after the oil news, Brazil invited Russia to do massive military drills, and yay! Russia did came, and ÚS ships started to stay very wide of brazillian waters)