Easy example: compare the Marvel "Civil War" comics to the movies. The former was critical of the military in a way that could not happen in any big blockbuster movie.
The question is why the people making the content in the US and China don't want to certain content. Is it because they're worried it won't be popular or because they're worried that it will be popular.
I can't prove anything (how would you?) but I tend to think in the U.S. it's the former and in the China the later.
You can, in fact, have critical views of the military in blockbuster movies in the US. But not if you want to use US military bases and aircraft and ships as sets for those movies, or to get support of the US military in making the movie. Depending on the particular movie, this could be a make-or-break deal for them (Top Gun, for instance, would be pretty shitty with stock footage of US aircraft carriers and aircraft instead of actual footage staged for the movie).