Bernardo Bertolucci's expressionist masterpiece of 1970, The Conformist, is the movie that plugs postwar Italian cinema firmly and directly into the emerging 1970s renaissance in Hollywood film-making. Its account of the neuroses and self-loathing of a sexually confused would-be fascist (Jean-Louis Trintignant) aching to fit in in 1938 Rome, who is despatched to Paris to murder his former, anti-fascist college professor, was deemed an instant classic on release.

It was, and is, a highly self-conscious and stylistically venturesome pinnacle of late modernism, drawing from the full range of recent Italian movie history: a little neo-neorealism, a lot of stark and blinding Antonioni-style mise-en-scène, some moments redolent of Fellini. And it was all framed within an evocation of the frivolous fascist-era film-making style derided by Bertolucci's generation as "white telephone" cinema. Add a dose of unhealthy sexual confusion and it's hardly surprising that it was one of the international hits of the year. It also offered the blueprint for the new wave of Hollywood film-makers to a different kind of cinema and a roadmap of new formal possibilities – not merely for those of Italian descent such as Francis Coppola andMartin Scorsese.

To be sure, Coppola's The Godfather, with its operatic qualities, seems on the surface to have more in common with Visconti's mature work (while the paranoid-realist spirit of Francesco Rosi hovers ever near), but Bertolucci became friends with Coppola, and his influence is palpably discernible in the formally adventurous The Godfather: Part II. Surveillance expert Harry Caul (Gene Hackman) in Coppola's The Conversation is a repressed Catholic and professional paranoid who has plenty in common with Trintignant's agonised Marcello Clerici. Meanwhile, Bertolucci's cinematographer Vittorio Storaro – who shot both The Conformist and Bertolucci's other 1970 masterpieceThe Spider's Stratagem – made his American debut on Apocalypse Now, and has worked with Coppola several times since, as well as remaining Bertolucci's DP (while also working fitfully for Warren Beatty).

There are other links. Marlon Brando, after completing work on The Godfather – something that reinvigorated his career and sealed his image as actorly padre padrone to the young ethnic method players who emerged from the set of that film and thereafter dominated serious American cinema of the 1970s – went straight to work on Bertolucci'sLast Tango in Paris.

Whereas The Godfather's producers had been fearful of Brando's reputation for destroying big-budget movies with his sheer unmanageability, and had reigned him in accordingly, Bertolucci was the first director successfully to accord Brando the privilege of near co-authorship: he knew that a creative Brando inside the Bertolucci tent was better than a destructive one outside. Brando's on-screen successor in the role of Vito Corleone, Robert De Niro, would follow in Brando's transatlantic footsteps to play the lead in Bertolucci's socialist-realist melodrama 1900 (Novecento), in 1976. Another memorable exchange was the actor Gastone Moschin; having played the fascist operative Mangianello in The Conformist, he was later cast as Don Fanucci, the comic-opera kingpin of the Black Hand in The Godfather: Part II, a growlingly menacing portrayal straight out of silent melodrama.

Some aspects of Bertolucci travelled less well. Some of his formal ideas were greedily consumed by American film-makers, while the radical politics and pointedly Brechtian alienation techniques were largely discarded. Thus the emotionally expressive colour scheme of The Conformist – principally evident in the honeymoon train-ride of Clerici and his blousy new bride, during which insanely unrealistic rear-projection and alternating blue and gold filters throw into doubt the dependability of Clerici's perceptions – are partially replicated in the colour-scheme of the two sections – past and present – of The Godfather: Part II. Its flashback sections are shot in ridiculously warm and nostalgic golds and sepias (the consoling colours of infantile memory and adult self-delusion) while the late 1950s present-day is rendered in icily comfortless blues and greys. Similarly, Taxi Driver's heavy reliance on the perceptions of Travis Bickle, the least reliable narrator in 1970s cinema, is evoked using many powerful expressionist effects that Bertolucci had made his own – but, again, with no concomitant importation of his political radicalism.

And Bertolucci, it turned out, would suffer a similar fate to all his contemporaries in the "new Hollywood". 1900 brought him closer to the fretful world of international co-production dictated by the new Italian film-financing laws enacted at the start of the 70s and – interesting though it remains – it stands as Bertolucci's equivalent to the movie brats' big-budget disasters, the films that knocked them off-course: Steven Spielberg's 1941, Scorsese's New York New York, William Friedkin's Sorcerer, even Coppola's Apocalypse Now. And, as happened with Coppola, Bertolucci's work was never again as interesting or as pioneering afterwards.