You are confusing censorship, with something else. The payment for those assets are incremental expenses — I repeat the Defense Department doesn’t exist to make movies more awesome; and I repeat Hollywood doesn’t exist to make critical commentary about the U.S. government. Hollywood allows the government of creative control in order to make more money.
There is no threat of violence, fines, or otherwise that is preventing anyone from making a critical film about the government (at least in the great country I am writing from), but when you do you can’t complain about government not supporting your film. These things do really exist in other places in the world, particularly in those places without an explicit right to freedom of expression.