Continuity mistake: In the subway, Lisa throws the earrings downwards. Cut to the next angle where they appear at Akeem's waist level and, oddly enough, flying up to his right hand, raised at chest level. This would only be possible if someone had tossed the earrings at ground level.
Continuity mistake: In the scene towards the end of the movie you can see the dog sitting by the piano. At that time the keys are revealed. A few seconds later the keys are closed.
Continuity mistake: In the scene where Akeem and Lisa are walking at night, and you can see the New York City skyline in the background. They visibly pass a certain area and the camera changes views, then goes back to Akeem and Lisa walking. They walk past the exact same spot as the previous shot.
Continuity mistake: When Akeem is about to be wed at the beginning of the movie, his bride-to-be is walking toward him on a rug. She is almost to the end of it, then the camera comes back to her and she is at the beginning of the rug again.
Continuity mistake: In the scene where Akeem just left after realizing his parents arrived, Mr. McDowell pulls a bill out of his pocket with Akeem's face on it. It is wrinkled when he pulls it out, but when Lisa looks at it it is a brand new bill.
Continuity mistake: When Akeem's parents enter the McDowell's house with the courtiers (the young ladies) they all wear gloves (it's winter time). Briefly, one of them can be seen not wearing gloves.
Visible crew/equipment: You can see bits of the camera crew reflecting on the carriages, when the metro-train leaves the station after Akeem has gotten out after Lisa refused to marry him (near the end of the film).
Continuity mistake: When Lisa moves to a different train carriage near the end, she opens two doors. She tries to slam the second door as Akeem is following her, but it bounces back and remains completely open. In the next shot, however, the door is completely closed, forcing Akeem to open it.