China has become a market so difficult to court. You want your movie to be released to the 1.3 billion population to make some coin off of. Not to mention having you movie released in China not long after your initial release would hopefully stop a good chunk of piracy that is rampant in China. The wall China has built around itself has shown some signs of waning but it's a long and slow process that is often baffling.
Pacific Rim wasn't a deep movie. The story, the world, the atmosphere, and everything built around the giant monsters fighting giant robots was only there to serve the action. Director Del Toro made a live action anime that many just assumed couldn't be done. And if you've seen the film you would know it was a fun ride of an action movie and not much else. Unless of course you're the Chinese military which of course you saw American propaganda.
In an official Chinese military publication op-ed Zhang Jieli said the movie was "deliberately" setting some action scenes in and off the shore of China. This was intended to "demonstrate the U.S. commitment to maintaining stability in the Asia-Pacific area and saving the mankind.". He continues to suggest that these movies could degrade Chinese military attitudes about their own culture since this film is clearly trying to suggest only the American military can save the world.
I guess I saw a different film where most governments purposefully distanced themselves from the giant robot program. And that the robots fighting in the South China Sea were an international effort including a Russian and Chinese controlled robot. Sure the two English speaking teams, American and Australian, were the eventual victories and saviors of humanity but that's a Hollywood size cliche not a Pacific Rim one.