Excluding Mexico is a huge disservice because Mexico actually has stricter gun laws than the US. Mexico's gun murder rate is over 3 times greater than that in the US.

I feel this is instructive because with all of the guns already in private hands in the US if they were banned outright today you'd end up with an enormous and uncontrollable black market. The same type of black market that exists in Mexico.

Even in the US now, the vast majority of gun crimes are committed with illegally obtained guns. Something on the order of greater than 90%.