Factual error: In the film, the train is hauled by diesel locomotives on a single track not electrified line. Since early 2000 the Trans-Siberian is double-track and fully electrified.
Factual error: When Natalie decides to rebuild the carburetor that Keith gave to her, she opens the rebuild kit and starts lying out the parts. The problem is that the kit is for a French Solex type 30 single-barrel carb, and the carburetor in the box is a domestic four-barrel.
Factual error: We're told over and over that Vicky is an expert on Barcelona and Catalonia, for she has written a thesis. She visits Avilés (Asturias) with Juan Antonio, where he tells her he was born a few blocks from there; however, during their dinner at night the actress mistakes and tells him that he's from Catalonia, instead of Asturian. Anyone with a such an expertise on Catalonia will know that. Besides, it's not real life, but a screenplay, so either Woody Allen screwed up, or the actress did.
Factual error: In the streetcar scene a passenger is a soldier wearing a US Army green uniform with a CIB, Comat Infantry Badge. At the time US uniforms were brown and there is no plausible reason for this US soldier to be in that country.
Factual error: Spider's club is shown on 125th Street in Harlem, but whenever the officers radio in the location, they say 184th & St. Nicholas, which is in Washington Heights over 3 miles north.