Even if the USA tomorrow was to have a blanket ban on all weaponry, little would change. There are so many weapons in the USA that it would be years (if ever) before those that wanted them couldn't easily get hold of them. Probably less easily than today, but still far from impossible.

Guns can be effective for years, and with the large borders America has, the small number that would be confiscated by the police would be replaced by the criminals with ease.

"Smart guns" (fingerprint ID, or better yet with an inbuilt tracker) might help eventually, but they'd have to be coupled with draconian penalties for having the old type of gun.

Unless something earth shattering happens (and let's face it, Americans don't blink when a gunman guns down Amish children), no politician is going to have the backbone to do anything about this in a meaningful way.