There is no real way to gauge the impact on contemporary American society of a macabre phase in North American history about which relatively few people remain aware. The Salem Witch Trials occurred in 1692 in response to mass paranoia regarding sorcery and the occult. Specifically, residents of this Massachusetts community lived in mortal terror of being accused of practicing witchcraft -- a crime punishable by death and the accusation of which invariably was grounded in nothing more than superstition and hatred. Neighbors who developed an intense hatred for each other, for instance, could accuse each other of practicing witchcraft, thereby ruining everybody's day.
In 1953, the American playwright Arthur Miller published a play, The Crucible, based on the events of 1692. While Miller's story was steeped in fact, the author having meticulously researched the era, the true target of the play was the 20th century equivalent of the Salem witch trials, the Red Scare and the phenomenon known as McCarthyism, for the Wisconsin senator, Joseph McCarthy, who sought fame and power by accusing others of communist sympathies. To Miller, and others, McCarthyism presented a modern-day parallel to the witch trials, and it was this observation that made the events of 1692 relevant to the modern age. By merely accusing somebody of being a communist, or of associating with communists, that individual's life could be ruined.
To the extent the Salem Witch Trials affected modern-day American society, it is that experience's psychological correlation to the propensity of people to engage in mass hysteria today, whether with regard to fears about terrorism, or with respect to the modern era's association with all-seeing/all-knowing surveillance systems. The lesson is to guard against ignorance and fear, as the two make a lethal combination.