...well, it IS a bygone truth that over the years, one form or style of entertainment inspires the next. As such, the Italian 'giallo' films, and associated horror films, have indeed inspired many of the American filmmakers, who have taken the horror film as their choice of venue, as early as the late '70's, on up to today's onslaught of horror films...
...however, if one really gives it some serious thought, the classic Italian 'giallo' films, themselves with their unflinching graphic visuals, seemed to, and could have very easily derived their inspiration from the old Grand Guignol theater shows of the early 20th century, with their dramatized acts of unflinching violence and bloodshed, which was perform on stage, in full view of it's audience....