You list tools to determine information, but this doesn't show that the information itself is cromulent.Artifact analysis, looking at records, reading articles from the time, there is actually quiet a good amount of information about it. Granted recording keeping was quiet as good then, but that wouldn't be enough to account for the discrepancy. Even mass shootings. The real cowboy and "Wild" West just do not compare to the stories we tell. What we think of today is really nothing more than the setting for America's own mythical legends and heroes (we have Cowboys in the West during the mid-19th century rather medieval knights in dangerous forests) that didn't become a widespread belief in the early 20th century when the Western genre, especially in literature, began gaining an enthusiastic audience. And the image of the cowboy is very heavily and very deeply rooted in modern American culture.
I'm skeptical of the claim that we're more violent than the wild west.