Social customs differ in different parts of the world. If we don't realize this, misunderstanding may arise between people that behave differently. In the United States, people are very informal in social situations. For example, they call each other by their given names when two people first meet. So do the young to the old. In China, it would be regarded quite impolite to do so.
Another difference is about what can be talked about in a conversation. A Chinese thinks nothing of being asked how much his coat cost while Americans think it impolite to ask such a question. A Chinese woman doesn't care if she is asked about her age. Politics, religions, as well as incomes are often talked about among Chinese. But in the United States these kinds of subjects are usually avoided in conversation.
Since there are many other different social customs between Americans and Chinese, the way that we behave and what we talk about requires our attention. If we keep these in mind, we will do it better and understand each other better.