Yes they exist, sure. Not everywhere though.
I mean... I was in Salt Lake City this summer and went to the range.
I could, as a foreigner, buy any rifle or pistol I wanted. No background checks involved, I didn't even need to register myself.
Gun ownership is fine when fopr recreation, but don't give me the bullshit argument about protecting yourself from the government. Given that the U.S. government can't even pass proper healthcare laws or educate its people let alone overthrow the democracy and create a dictatorship. Not to even mention the fact that if a dictatorship ever comes to be in the U.S., it'll be self-inflicted and not forced.
The self defense argument is not that strong either. Sure home defense, I can get behind that to some degree, but having a 9mm glock protecting your house or a 7.62 FN SCAR will seriously not make a difference and I hope you can argue that having high powered rifles out and about isn't that ideala situation considering you can blow the tits off of someone with that thing from 800 metres away and there's only so much police weapons can do about that.
Open carry to protect against an active shooter situation? Hilarious. Even police officers, fuck me even regular army infantry personnel aren't equipped and/or trained enough to handle an active shooter event. That's why there are tactical response teams to begin with. And you're telling me 52-year-old uncle Bob from Tennessee, the old cowboy indoor range tiger, is capable enough to stop a shooter at church on Sunday next week without killing a few more extra innocents? That's not sensible at all.
Besides that, there have already been instances when an active shooter event was happening where civilians were carrying weapons... That turned out to be a significant clusterfuck because as soon as there were multiple armed people out and about nobody knew anymore who the shooter was in the first place.