Dear Wendy is one of the strangest love letters ever to float my way. It was written by Lars von Trier and posted by his Danish friend, Thomas Vinterberg. The stamps are European, but the envelope was franked in Estherslope in the heart of the United States.

You won’t find this dusty mining town on any map. As far as I know von Trier has never set foot in America, and his recent trips down Route 66 (notably Dogville) are almost drunk on that proud fact. Dear Wendy is not the most convincing film these Dogme veterans have made. It’s not much of a letter, either. But it’s the only interesting new missive on offer this week by a long stretch.

The clever tease is that Wendy is not a girl. She is a pearl-handled 6.65mm double-action revolver. Her doting admirer — whose confession is scratched out in ink during the opening scene — is a thin-faced 18-year-old loner called Dick (Jamie Bell).

Gun and boy meet in a second-hand shop, but it is not exactly love at first sight. Dick buys the “toy” pistol as a joke present and is horrified to discover that it is a vintage fire- arm. How this pretty weapon reshapes his life is the unsubtle point of Vinterberg’s satire on American gun culture.

Dear Wendy is a country mile from the juddery, hand-held realism of the director’s first film, Festen, but mere inches from von Trier’s obsession with gutting America without actually having to go there. The result is that we get the worst of both artists. Vinterberg is not the most persuasive surrealist, and von Trier needs to travel further than a reference library if he wants to script a satire that bleeds.

If I sound unduly harsh it is because these two film-makers have been responsible, in Festen and Dogville, for 283 minutes of the best cinema I have ever seen. Dear Wendy simmers with similar dramatic promise. Gathering together the teenage losers in his small town, Dick starts a secret gun club called the Dandies in a disused coal mine. “I think pacificists with guns is a really great idea, ” declares one young delinquent scruff. The irony is delicious. The gang members start dressing like Duran Duran and turn the mine into a “temple” where their weapons can be properly adored. They create their own laws and etiquette, fill mining shafts with rugs and candles and study books about exit wounds.

They become brilliant sharpshooters, but most of all they are miraculously transformed by fetishism, and the erotic power of their lethal lovers. They are no longer the local misfits. They get jobs and look customers in the eye. The jukebox suddenly starts playing the Zombies’ greatest hits. Flat-chested Susan (Alison Pill) even sprouts a pair of impressive breasts which she proudly exposes to the embarrassed Dick. They no longer fear. They march through the main square untouched by the paranoia that seems to infect every other local.

Even their use of language changes. The Dandies affect a Brideshead Revisited stutter, and change the word “killing” to “loving” to soften the ultimate point of their deadly “friends”. Dear Wendy is clearly an exhilarating rites-of-passage film if you are a psychopathic, trigger-happy New Romantic. Poor old Jamie Bell. He acts his socks off. But the melodrama is dismal, the consequences predictable. The satirical psycho-drama gives way to a silly Butch and Sundance shoot-out when the Dandies are forced to square up to the usual squad of cynical cops.

The questions Vinterberg and von Trier ask are decidedly bizarre: Is this the kind of idealism that shaped America? Is this how the West was won? Answers on a postcard please. Address? Return to sender.

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