To summarize, I do not think the US has an unhealthy relationship with guns a small percentage of people are whack jobs and do shit like this. Why are you so willing to tell everyone who has a gun (and for the record I do not now nor ever have owned a gun, I do not see the need or appeal of them) they cannot have one for whatever reason they own one.
As to the police state comment, there are tons of guns in the US now, it is not like they go bad. So even if we stopped selling new ones, how exactly are the old ones to be collected? Add to that, you can make one now with a 3-D printer, a very crude one, but it is only a matter of time before you can make better ones that way.