In Brazil, there is this neopentecostal church that claims that demons exist and possess people. Usually, the priest will say something to make the demons angry. The people surrounding the priest are allegedly possessed and they start throwing up and cursing and even their voices change.
The priest then proceeds to exorcise everyone.
Whether the people are truly possessed, I am not able to tell. What I can say is that the videos I saw on Youtube are truly frightening and that if the people are faking to be possessed, they do a much better job than Hollywood actors do.
I have heard these churches exist in the south of the United States, as well, and have a huge following.