What orgs have a good track record stopping abuse by the US Government?

I was thinking about it, and most everyone that has criticized the US government have quietly disappeared after the news cycle is over. Every whistleblower gets arrested or escapes to another country. Julian Assange and Wikileaks has been entirely dismantled and stopped at this point. The groups that remain will complain in a news segment and deliver nothing else. The incumbent advantage in democracy has kept politicians in charge that don’t ask for serious change.

Ultimately, many social problems are never addressed. Does the U.S. government have any effective check and balance?