Sure there will be regulated and licensed gun owners in America, who will be restricted to 5 round mags and mags that can't easily be removed. Robots will deal with the freedumb loving and paranoid, there will no shoot outs with big guberment agents. They will be in a van parked down the road.
The federal government can regulate guns under the constitution and will, over time the cost and bother of gun ownership will increase. America already banned assault style weapons and can do it again, Canada can provide a list of over 1500 specific makes and models and I can supply a definition as any semi automatic rifle with a large magazine capacity and a removable magazine. Register it and pay a fee per gun, or take the cash and the government takes the gun. Many of the hard core dangerous gun freaks won't be allowed to own guns anyway, they will be on the domestic terrorist watch list and will also be taking the bus.