Again, comparison to other developed countries proves there are.
Edit to answer to the comment below: think what you want. Don't try to convince me. I'm skeptical, you're not. Write to your legislators instead of here. Write your own blog posts.
In terms of number of guns, no other country is. That's the point: other countries made decisions and implemented policies to severely restrict access to guns, and the predictable result today is that there are far fewer guns and much less gun violence.
The decision to restrict guns is a long-term decision - it won't reduce gun violence overnight, but it will reduce gun violence over decades.
But I think you're wrong about the path that restrictions would take in the US: the slowly boiling a frog approach won't accomplish the goal, anything too quick, sharp and raw will merely spark the 2nd American Civil War during which "gun violence" will go way up. And most any restriction scheme will increase gun violence, if only on the part of the authorities using force to seize guns and the like.
Maybe in the long term public attitudes could be changed, the 2nd Amendment repealed, and the path you envision might happen, but that's the work of generations and will require a reversal of the renorming of gun ownership we've seen in the last quarter century (I take Florida's 1987 establishment of a shall issue concealed carry license regime as the start; today 42 states have them, de facto or de jure).
If heterogeneity was a factor, surely homicide rates would be climbing in countries like Canada and Australia that have the highest immigration rates in the Developed world[1]. They are not.
Number of guns is precisely the factor at the heart of the issue.
[1] http://en.wikipedia.org/wiki/List_of_countries_by_net_migrat...
