If the reference point is the radio broadcast in 1938, I think that one could argue several points as to why there was panic and hysteria inducted. One one hand, the time period was of significant mention. Fascism in Europe was at a dominant level and there was a fairly strict division in American society that indicated fears in America that this would spread to America, as well as an equal force that demanded no intervention in such a manner. The radio broadcast induced panic because it helped to trigger the fear of both sides that there was a realistic chance that America could be overtaken. Similar to the book, the radio broadcast also induced a level of panic because of the lack of response to the invasion of the aliens. The idea of outside life being able to land on Earth and an inappropriate response to it helped to enhance a sense of fear and panic.