Above I gave FBI sources murder rates in the USA, with a population of 300,000,000.
A. Of the countries you mentioned, Japan has the population closest to the USA at about 127 million. Not even 50%. Ethnically, they are homogeneous.
B. All have histories of incredible violence toward their neighbors, except for Aussies and Canadians.
C. Aussies and Canadians live in countries where there are very few people per land area.
Concluding that only the difference between the USA and another nation's gun laws is the ONLY reason that 8,000 gunshot inflicted murders of 300,000,000 mostly armed citizens is narrow-minded.
First, the homicide rate with guns is closer to 11,000, not 8000. and sorry, the 20,000 suicides really are a problem. Japan had 11 gun homicides in the last year I can find numbers for. The United Kingdom had 48, Germany had 258. Even accounting for smaller populations, we have a horrific homicide rate for a developed nation.
Second, history is irrelevent in this context. We've murdered Iraqis, Vietnamese, Filipinos, and Native Americans by the hundreds of thousands because we've wanted their shit, too.
So, sorry, we have a real problem. And I'm getting a little tired of watching preschoolers being wheeled out in body bags so you can compensate for your tiny dick.