"What are you waiting for?" ~ funny culture difference

This is a story when my Japanese friend came to the US for the first time.
My American friend and I took her shopping in his car, and then we dropped her at her apartment. After she got out of the car, she was standing by the car and watching us. My American friend said " what is she doing?" He was waiting for her to enter the apartment.

It was funny. I told them it's a culture difference. When American people dropped someone off, they wait in a car until that person enter a building. On the other hand, Japanese people do the opposite. A person who gets dropped off will wait and see off his/her friend until the car is gone, perhaps while bowing. This is the Japanese way of showing their gratitude toward a person who gave them a ride. However, the American way might be more reasonable because the person who gets out of a car might face a danger or lost/forgot their key for their building.

Anyway, if you don't know about this difference, funny things might happen. Both of them would have been watching each other and waiting forever...