In late August, I took my parents to see Once Upon a Time in the Middle East in their small-town cinema on the mainland. Built around an unnamed conflict widely understood to be the US-led Iraq war, the film has become the kind of phenomenon no marketing budget could buy, projected to reach 2.5 billion yuan (US$372.5 million) largely through word of mouth. Its Hong Kong and overseas release will revive geopolitical arguments over a Chinese commercial film entering a narrative world long...