In 1976 George HW Bush declared that the CIA wouldn't manipulate the media anymore but this NYT article from a couple months later shows the feds backpedaling on that promise, along with some specific examples of media manipulation from the time: http://www.nytimes.com/1976/04/27/archives/cia-will-keep-mor...
I haven't found any evidence of post-Cold War media manipulation of this sort, but I don't think American trust in the media has ever fully recovered since those days.