There were not red stars on every second building in Hungary in the communist/socialist era. They were only on important official buildings.
Young Zsuzsi seems to learn complicated English very quickly.
Suzanne pulls way more stuff out of her overhead closet than could fit in there.
Suzanne first arrives in Los Angeles in 1955, one house has an eighteen-inch television satellite dish strapped to the chimney.
International trains from Hungary would very rarely have been steam trains in the 1960s.
When George visits Zsuzsi on her birthday, bringing her the doll, as he drives his car in, the number plates can be seen briefly. They are the new type of plates used in Hungary from the early 90s to 2003. Besides, it begins with OT, a special plate for old timer cars (hence OT).
In 1955, Suzanne's father is shown with a bottle of Stolichnaya Russian Vodka which was not imported to the United States until 1972.
A graffiti slogan in Hungary emphasized in the film that reads "Le az Amerika Imperializmussal!" ("Down with American Imperialism") is accurate only for the 1950s, but not the setting of the film in the 1960s when Hungary became more liberal and anti-American and anti-Imperialism public slogans became more rarer.
Much of the traditional rural background music, including the music over the credits, is not of Hungarian origin at all.
When the 'Orient Express' with Zsuzsi arrives in Budapest, we see a sign on the train car indicating that 'Wienna' is among the intermediate stops of the train. The Austrian city of Vienna is called 'Wien' in German (or Vienne in French or Bécs in Hungarian). It's not called Wienna in any language.