Hi CapnMac, I really liked this when I first ready it! Its extremely powerful if it can be verified.
A very quick search came up with this article showing the 5 major cities with the most murders in 2017:
https://www.usatoday.com/story/news/2018/02/19/homicides-toll-big-u-s-cities-2017/302763002/
The total of these 5 is 1886 murders in 2017.
From wikipedia I come up with a total number of murders in the USA at 15,696 from 2015
https://en.wikipedia.org/wiki/List_of_countries_by_intentional_homicide_rate#By_country
So the total for the US when removing the 5 cites with the most murders is 13,810.
From the above Wikipedia link the total number of murders in Japan is 395 from 2014.
I'd be really curious to see where you got this information from. I really want it to be true!
Im also pretty skeptical of the argument in the original post and map that more guns equal less crime on a global perspective. I personally think it's primarily a combination of two factors:
1 - The society must be high trust. As George P was alluding to this is usually the result to ethnic homogeneity along with a similar history and religion.
2 - The society must be high IQ. An individuals IQ is the single best predictor of all problems in society from of course violent crime to single motherhood to welfare consumption.
The USA is of course a mix of these two. At one extreme you have the high trust / high IQ regions of America such as East Asian and Jewish communities and on the other you have the 5 cities referenced above. As others have said its a very complex situation that no one on either side seems to want to have an "honest" conversation about.
Thanks, Dan