Watching a movies at a theater

I like to watch movies in theaters. A nice thing about living in the U.S. is that the price of a movie ticket is cheaper than in Japan. After going to a theater several times, I noticed one thing. The audience is much more active here. On one occasion, an old lady sang a song along with the melody that played in the movie. People sometimes talk to or encourage the movie characters. This may happen only in my neighborhood, but this never happened in Japan. I feel I see an aspect of the cultural differences between the two countries.