Easily countered with the fact that they're largely available still. If they're not available for sale, or in their neighbors garage, they're not available for stealing.
Goes with above. But I'll sweeten the pot.. 82% of weapons used in mass shootings have been legally purchased.
https://www.msnbc.com/msnbc/most-guns-mass-shootings-obtained-legally
I'm glad you brought up drugs actually. Drugs are addictions. Tougher laws on drugs mean exactly nothing, as no one thinks about harsher penalties, just if they're not going to have the shakes when they wake up tomorrow. Guns are not addictions. Tougher laws would work, just like they do, and have done with the harsh penalties of killing a cop.
But also; look at the stats of what we have already. 133 mass shootings, 11 private citizens stepped up to combat. Less than one in ten will do something about it. So you say more Americans should arm themselves. You're giving to both sides there, so at best it's a net neutral. And In this day and age, are you really so naive as to say every American should always be carrying around a weapon?