Potential Fourth World scenarios are a rare breed in the cinema. Meetings of the First World and the Third tend to be seen in terms of "strangers in a strange land" or show disastrous encounters (Mosquito Coast, Castaway, etc.) as Americans/Europeans fail to adapt to new circumstances.
There are, however, some exceptions:
Black Orpheus (1958)
Retelling of the myth of Orpheus, set in Rio de Janeiro during the carnival. Great Bossa Nova soundtrack.
Fellini's Satyricon (1969)
"One critic of the time called this one of the most 'Jungian' movies ever made. There sure does seem to be a lot to compare with the archetypal approach. What Fellini does best is present an ancient Rome totally different from the old Hollywood historical films we have become so secure with over the years. At times the ancient Romans seem like modern city dwellers in our time, then suddenly, they appear like an alien culture from the farthest star. This film affected the style of a lot of science fiction and fantasy films to come. Watch Ridley Scott's Blade Runner and see if the future city in it doesn't remind you of Fellini's ancient Rome."
R.T. Gault, Absolute Elsewhere
The soundtrack is an eclectic mix of Fellini's regular composer, Nino Rota, along with music from Andrew Rudin, Carlo Rustichelli, Tod Dockstader, Ilhan Mimaroglu. Electro-acoustic composer Mimaroglu is notable for having made the remarkable anti-war album Sing Me A Song of Songmy with trumpeter Freddie Hubbard a couple of years after Satyricon.
Apocalypse Now (1979)
Not necessarily the film itself but the soundtrack. The blend of Mickey Hart and Billy Kreutzmann's River Devils percussion ensemble with Patrick Gleason's synthesisers and Carmine Coppola's choirs create an incredible and successful conjunction of the primitive, futuristic and sophisticated. (Gleason was synthesist for Herbie Hancock's electric jazz group in the early '70s.) An album of the Rhythm Devils' sessions was released on Rykodisc in 1989.