Let me try to understand this - lots of your criminals have guns, while very few decent citizens have them. Statistically speaking, if a criminal targets a random citizen, the chances are very low that that victim has a gun. Thus letting citizens have guns or banning them from decent citizens would make very little difference.
When people (inside or outside the USA) say the USA should make it harder for people to get guns, they mean criminals as well as decent citizens. If you implement measures that reduce criminals' access to guns, ordinary people have less need of them. It would take time for the current circulation of guns to be significantly reduced, and there would always be a certain element in the criminal world who are armed, but you could make a start by controlling access to guns. Useful ideas would be mandatory registration, serial numbers and ballistics samples, tighter controls on people buying guns, much tighter controls on those making or selling guns, high taxes on sales, and regular inspections of registered guns (to make sure the owner hasn't sold it on).