In another decade or so weapons could be made publicly available that don't kill that are the same size as current weapons or smaller that are actually better at defending you from an attack than a conventional gun in many circumstances.
Take this weapon, it over the years to come could protect you from several crooks with guns in just a split second and you wont have to have killed anyone. I can see weapons that can knock someone down and immobilize them instantly coming before too long. At that point society even in the US might be prepared to substantially change their gun laws to only being allowed to carry "non-lethal"- http://en.wikipedia.org/wiki/Vortex_Ring_Gun
EDIT- They've already developed this weapon to carry an incapacitating agent (as it says in the wiki article posted above)-
"The vortex ring gun is currently being developed. It fires a blank cartridge into a barrel which widens towards its muzzle. The pressure accelerates the air or gas in the barrel at high speed and it becomes a high-speed travelling vortex ring.
The weapon has been proven to knock down a 75 kilogram (165 lb) human dummy from 10 meters away with a single shot; military use will need a range of more than 20 meters.
This system will be designed to be handheld for single shots and mounted for multiple shot systems. It is planned to mount the vortex ring gun on a GL-6 repeating revolver 40 mm grenade launcher, or on the MK19-3 automatic 40-mm grenade launcher.
Firing at 10 shots per second resonates with body parts and causes a stronger effect.
An incapacitating agent can be injected so it mixes into and is carried by the vortex ring."
Incapacitating agent- The term incapacitating agent is defined by the U.S. Department of Defense as
"An agent that produces temporary physiological or mental effects, or both, which will render individuals incapable of concerted effort in the performance of their assigned duties."
Lethal agents are primarily intended to kill, but incapacitating agents can also kill if administered in a potent enough dose, or in certain scenarios."