•Answer•
A weapon of some kind which was reasonably cheap to manufacture and easy to use, and which would knock people out as fast and from as great a distance as a gun would do, without causing permanent damage.
The dart guns we use for wildlife won’t do, because the dart sometimes bounces off, they’re dose-critical, and they take a couple of minutes to knock the target out. But there are already sleeping drugs on which it’s almost impossible to overdose - the more you take the longer you sleep, but you don’t die - so it just needs faster action and a reliable delivery system.
That’s the only way I can see that the US could get out of the cycle of “I need a gun to defend myself because I’m scared of you because you have a gun”, and then the only people who would need a *lethal* weapon would be those hunting for meat or pest-control or to cull over-populated species.
•I hope this help•
