One, they didn't eliminate guns in all of those societies. Even Japan still has some, and if you want to suggest going back to Tokugawa days with the requisite loss of all civil rights as a basis for their current society as a method to have a similar one in the US, I'll have to disagree. The UK, Canada, Germany, Japan and Australia all still allow ownership of firearms that can be used in mass murders. Australia recently had one with a shotgun. Australia still allowes possession of handguns 9mm and smaller. Canada still allows possession of handguns 4" barrel and larger. The UK's last gun mass murder was committed with a .22 bolt action rifle and a double barrel shotgun.
Your basic premise, "Eliminating guns in all the societies I mentioned", is simply incorrect. They didn't do any such thing. They also didn't eliminate mass murders, either with firearms or by substitute methods using common, easily available objects, or those less rare by methods such as bombing.
Regardless, if the solution you propose is to eliminate guns in the US, you're tilting at windmills. None of the citizens in those other countries have a Constitutional right to keep and bear arms.
