Criminality generally is much lower in Japan for whatever reason.  For this reason it is particularly poor comparison.  Some of the ethnic nationalist types like ramzpaul will claim that ethnic homogeneity is largely responsible the phenomenon.

Japan does seem to lead the U.S. by basically infinity in sarin gas attacks on subways.  When someone is genuinely interested in terrorism we are lucky that guns are an option for them compared to a lot of other methods.  The fact of the matter seems to be that nearly every 'terrorist' act almost anywhere is actually a false flag which allows TPTB to accomplish some project they want to do, or (luckily for us here in the U.S.) a bogus hoax made possible by a consolidated, compliant, and complicit corporate media.