Why is there a perception that Americans clap at everything?

Americans clap (or "applaud") to show agreement, support for a person or issue, joy, or praise. It is considered the proper way for a crowd to interact with those on stage. But it's not new, and it's not even American in origin. In fact, it's a very old custom, that goes all the way back to ancient times-- we have evidence that the Romans used it, and so did other cultures. Also, in European and American culture, applauding is considered a more appropriate method than shooting off a gun into the air-- this is still one of the common rituals in certain Middle Eastern countries for showing joy and approval; in American history, it was used in Texas (and in Mexico) in the 1800s, but is not legal today.