Heavily favoured to pick up several Oscars on Sunday, Three Billboards Outside Ebbing, Missouri is set in a fictional town in a fly-over state where the angry Mildred Hayes demands to know why the local police chief hasn't solved her daughter's murder.

Reviewing it last November, I gently suggested that director and writer Martin McDonagh, a Londoner of Irish parentage, had not conquered the American heartland nor wrestled its issues of race and class to the ground. Ebbing, filled with nasty hicks and token black citizens, plus a whole lot of people who seemed to have wandered in from some much larger and more liberal place, did not ring true, but I was cautious about denouncing the film's social geography: After all, I've never been to Missouri.

As the film racked up four Golden Globe awards in January, including best picture, and then snagged seven Oscar nominations, something of a backlash set in. Mainly, critics complained that McDonagh's blackly comic film redeems a viciously racist police officer while failing to create fully rounded black characters. But some American commentators, perhaps stung that a Brit would presume to analyze their country's malaise, offered a more complex critique, decrying the film's social setting as false.

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"It's like a set of postcards from a Martian lured to America by a cable news ticker and by rumors of how easily flattered and provoked we are," Wesley Morris wrote in The New York Times, pronouncing Ebbing as real as Narnia. Interestingly, the name of Ebbing's presumed setting doesn't appear in that article nor in the film itself: Although actually shot in the small town of Sylva nestled amongst the mountains of North Carolina, Three Billboards is supposedly taking place in the hilly forests of southern Missouri. Three Billboards is a movie set in the Ozarks.

In my Canadian childhood, that very word was a slur; to demand of a classmate if he came from the Ozarks was to imply he was backward and ignorant. We may have been vague about the geography, but in an era in which we ran home from school to watch The Beverly Hillbillies or quaffed Mountain Dew on summer days, we knew that American mountain people were contemptible stereotypes.

Pondering the reaction to Three Billboards, I began to wonder how the film was playing in Missouri itself. It was only as I researched that question in local Missouri papers that I began to encounter references to the Ozarks and the light bulb finally went on.

When I talked with him on the phone this week, Dan Kelly, a Kansas City journalist and author who has also lived in rural Missouri, told me that Missourians would instantly recognize the setting in Three Billboards. He had barely noticed that the film doesn't identify the Ozarks by name.

"It seemed pretty familiar to me," he said. "I thought the characters were pretty accurate. There is a lot of racism in towns like that: I've heard people talk the way those people talk. … The town was exaggerated, but it's a movie." Still, he shared my hesitation about the few black characters scattered through the film, confirming my impression that rural towns in his part of the United States are either almost uniformly white or have historic black communities.

I had called Kelly because he had written a piece in the Kansas City Star identifying "Ozarks Noir" as a trend: There's the Netflix series Ozark, about a Chicago fraudster who escapes south to a rural community where all sorts of awful things happen, and the 2010 Jennifer Lawrence drama Winter's Bone. Based on the novel by Daniel Woodrell, it features an impoverished teenager who must support her younger siblings and mentally ill mother while searching for her long-lost father, an ex-con.

The genre, sometimes referred to as "country noir" and stuffed with meth dealers and dysfunctional families, doesn't offend Missourians, Kelly said: "Even if they are negative, people enjoy it. They don't associate themselves with it."

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McDonagh, meanwhile, was recalling a generic American setting when he wrote Three Billboards: He has told interviewers that he was travelling across the South by bus 20 years ago when he saw the three billboards with their plea for justice – but he can't remember what state it was in. And his producer Graham Broadbent has recounted how hard it was to find the right place to shoot the action: the one-street town of Sylva won out because of its look – and because North Carolina, unlike Missouri, offers tax credits to film productions.

Of course, McDonagh has opened his cultural parachute and floated into exotic rural territory before. Living in London, he first made his artistic reputation as a playwright with darkly comic dramas set in his parents' Irish homeland – in particular, his father's native Galway. His Connemara trilogy, including The Beauty of Leenane, A Skull in Connemara and The Lonesome West, was filled with colourfully violent characters and impoverished eccentrics, not exactly poster people for Tourism Ireland. The plays have been celebrated around the world and in Ireland itself, but McDonagh has sometimes been criticized there as an exploitative expatriate.

So how do Missourians react to Three Billboards? Local reactions from columnists and online commentators are mixed; some say the film accurately depicts the violence and the prejudice they see in their midst, while others dispute this characterization, complaining Hollywood and the coastal elites who appreciate the film view Ebbing as a trope, anyplace, flyover state, USA. That American regional lament about how all storytelling power resides in New York and Los Angeles may sound painfully familiar to Canadians, who similarly are seldom given the opportunity to represent themselves in popular film.

But the debate about the accuracy of Three Billboards is mainly taking place among urban Missourians. Kelly points out that people in towns that feel like Ebbing – towns such as Warsaw, Mo., where he used to live – probably haven't seen the film: If they even have a local cinema, what is playing is The Last Jedi, not some dark art-house comedy.

Still, Kelly liked the movie and will be rooting for Three Billboards on Sunday night: "People have pride in the state. Even if it wasn't made by Missourians or filmed in Missouri, it's our film."

For better or worse, local geography gets defined by cosmopolitan movies.

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