In the course of promoting his new film, Melancholia, earlier this year, Lars von Trier said something intriguing. No – not the oafish faux pas at his Cannes press conference, duly whipped up into the year's silliest non-controversy. Altogether more worthy of note was an interview he gave a fortnight before, and the admission that the director himself was unsure about his lush new confection.

"I may have made a film I don't like," he lamented. "This film is perilously close to the aesthetic of American mainstream films."

In arthouse circles, he might have been better off saying he was a Nazi. But though his confession did involve a typical flourish of hammy overstatement, it's not so far from the truth. Much of Melancholia is high-gloss indeed, starring a couple of game, big-name Hollywood actors (Kirsten Dunst and Kiefer Sutherland), kept company by a smattering of special effects and a breathtaking opening montage in debt to photographer Gregory Crewdson, famed for his lavish portraits of US suburbia.

In truth the result is a little too ravishing (and slow) to be filed alongside I Don't Know How She Does It, but you get the gist. Made by a Dane 50 miles outside Gothenberg, Melancholia may just be the year's best American movie.

Of course, lurking in his back catalogue Von Trier has his trio of even more explicitly American stories. Dancer in the Dark, Dogville and Manderlay all take place in one of the 52 states – or soundstage versions thereof – with the man behind them confined to Europe by his fear of flying. None had anything very flattering to say – a source of annoyance for patriotic US critics, who found it a bit rum to have a country's failings appraised for them by someone who hadn't actually ever been there. It's a good point although, as with everything to do with Von Trier, there's a counter argument – in this case that you don't need to have had your passport stamped by a scowling customs officer at JFK to have felt America's influence, or come to a view about capital punishment or the dark underside of smalltown values.

Von Trier's fixation with America hasn't only – or even most importantly – been restricted to setting his movies there. There's scarcely a genre familiar from Hollywood he hasn't dabbled in. He's done noir, science fiction, Sirkian melodrama, the musical, cabin-in-the-woods horror. His cultural promiscuity is part of what makes him so interesting. For all that Hollywood and international cinema often feel walled off from each other, the grey zone where they collide is a fascinating place. And that's exactly where you'll find Melancholia.

It's not just the slick visuals and relative lack of Von Trier-ish rough edges. Having flirted with so many other genres, what could be more definitively Hollywood than a big-budget disaster movie? There lies the very gooey essence of corporate film-making, every Armageddon and The Day After Tomorrow a lesson in how it's always darkest before dawn, and the sanctity of the lantern-jawed hero. Geographically Melancholia's location is never pinned down, but once you know the end of the world is nigh, Hollywood can't help but come to mind. We assume that when the news turns bad Bruce Willis or Will Smith or even Dennis Quaid will come to save the day.

Except they don't. In Von Trier's world, heroes have always been a dead loss. For all the complaints about his treatment of women, it's the male leads who are revealed as bastards or inadequates (or inadequate bastards). And here, in the space where the he-man should be, we have instead a depressive blonde bride, played by Dunst with a truly ferocious realism. Von Trier may have had to fake his American settings, but Dunst's Justine is a character who could only have come from both director and star knowing the ground first-hand.

If you squint, Melancholia can pass for a night out at the multiplex – but crucially, in the genuine article there's meant to be not just glitzy spectacle but optimism. It's really the whole point of the exercise, and the defining quality of so much about America. Whereas at the heart of this film, Justine exists beyond the reach of medication or even rousing third-act pep talks. Her presence turns Hollywood's whole logic on its head, even as Von Trier appears to present his most user-friendly movie yet – a glorious act of subversion in a film that's at once an homage to Tinseltown and a brilliant Trojan horse.