Of course, not all people in the United States have the same attitudes or customs when it comes to giving gifts. However, there are some customs that are fairly general to most Americans. Let us look at two areas of customs.
First, we can talk about the occasions on which one gives gifts. There are many occasions on which gifts are expected. On some of these occasions, only family members and close friends are expected to give gifts. Other times, more people are expected to give. The major family-only occasion is Christmas. It would not be appropriate to give a Christmas to a casual acquaintance. There are some exceptions to this. It might be appropriate to give some sort of food to friends at Christmas. It would also be acceptable to give food to coworkers, though this should usually be given as a group present unless there is someone at work who is particularly important to you in a professional sense. The major example of an occasion on which many people are expected to give gifts is a wedding. In general, it is expected that everyone who attends a wedding will give some sort of gift to the couple. There are many other occasions on which people give gifts. Prominent among these are bridal and baby showers, house warmings, and graduations.
Second, we can talk about customs about how the gifts are to be presented. In essentially all cases, it is required that the gift be in some way concealed. We do not simply hand a person their gift. Instead, we take care to wrap it, generally in some way that makes it look attractive. Many Americans expect that gifts they give will be opened in their presence.
There are many other aspects to gift-giving in the United States, but the occasions and the ways of giving the gifts are the most important.