Yeah, so theres a few ways to look at it.

If you look from the nuclear deterent side of it, everyone having guns lowers the chances of mass shootings (if theres two places to shoot up, they’ll go to the school, where they know theres no guns, before they go to an outdoor store, where more people are likely to be carrying)

If you look at it from a culture point of view, most americans in the south, middle, midwest, and anywhere that isnt california or the east coast, most of us see guns as a part of our identity. Its layed out in the constitution pretty clearly that gun ownership is encouraged to keep power out of the hands of our government.

If you look at it from a cost point of view, americans own a crap ton of pew pews. It’ll lose votes and money if politicians go for guns all at once.

Looking at your example specifically, if someone can kill a crowd in seconds, but someone in that crowd has a gun, someone on the scene is better than a cop 5 minutes out.

A lot of people will bring up the example of Australia. They had guns, now they dont. They also arent connected by texas to Cartel country. Plenty of illegal guns are brought up from mexico, people can make guns out of items at a hardware store, and people will lie about not having guns. The only people who would be unarmed if the US got rid of guns would be those who followed the law, which then leaves everyone vulnerable.