The OP does raise an interesting point in that you don't really see any more "uncontrollable psycho killers" like say Tommy DeSimone or the Gemini crew or Gaspipe. Where'd they all go?

My guess is that those guys weren't really all that berserk to begin with; they were just capable of killing casually and were in an environment in which they were able to do so. But they weren't the runaway freight trains that they have been depicted as. They are still around, but have adapted. I think Montreal proves that the potential for that sort of mayhem is still around; the guys in America just don't do it because it's too hard to get away with, not because they are any less murderous than they used to be.