Competitor lobbying doesn't even enter into it, I'd guess.

The US State Department won't tolerate Americans being exposed to media that doesn't adhere to its view of the world. What large groups of Americans think - and vitally, the bounds of what they are permitted to think - is a national security 'issue' in the eyes of the state. No such problem exists with Facebook, cable news, the establishment newspapers, etc. As Chomsky teaches, propaganda is equally about what isn't in the news.