As an American, I am always interested to see how Americans are portrayed in European films, particularly films made prior to WWII and in the years immediately following it.
The American in this film is portrayed as a vulgar contrast to the more sophisticated Europeans on board the train. He is a boozing, whistling, skirt-chasing Italian-American GI with a New York accent. (Why are they always from New York?) He is contrasted with the British passengers in two notable ways: First, his passion for the fairer sex is more overt and he comes across as wolfish in his pursuit of the young women in the film. This is contrasted with the discrete way in which the adulterous British couple on board the train are conducting their affair. When the two young French woman spurn his attempts to have a drinking party with them in their sleeping compartment, one says to him "We no longer wish to be liberated!" or words to that effect. This is a revealing statement about how the American military presence in postwar Europe was wearing thin the patience of Europeans.
Second, the magazines this American GI reads are prominently displayed so as to ensure that the audience can see them. They are the standard popular American mediocrities of the day: Saturday Evening Post, Life Magazine, etc. This is contrasted with the more scholarly (albeit boring) readings of bird-watching Britisher sharing his compartment.
Overall, the American in this film is the stereotypical boorish American so common in European films of this era. His portrayal, however, is not worse than Hollywood's stereotypes of Europeans.
Please note that this is not a criticism, but rather an observation. Americans are not singled out for criticism; the film traffics in several stereotypes (the cheapness of Scotchmen, for example) and does so mainly in a vein of comedic irony. Even the British get their own send-ups in this film.
