I don’t think you fully grasp my question. I am asking for an expression that dictates a certain circumstance such as what I described in the question. It is not about culture as it may appear. As you can read in many answers down below, it seems people don’t quite understand the real intention of it. But I can’t hide my feelings that you’re being judgmental. Nonetheless I agree with you in terms of the importance of understanding American culture and its characters in learning English.