I don't think it's the availability of guns in the US that produces nutjobs (I use that phrase reluctantly as I work in psychiatry), but the accessibility of guns that allow these people to harm or threaten others to reach their own ends. In other words, it's the culture of violence that exists that is the problem, the fact that firearms are readily available just means the wrongdoers can be even more violent. The US probably doesn't have any larger a problem per capita percentage wise than anywhere else, but it does have a reputation for violence. I have no idea what the answer is, but I would think tighter gun laws would be a good start.
I remember taking a road trip with a couple of friends back in the early nineties. We had planned it to be the trip of a lifetime, three months travelling from east to west on a shoestring budget. We touched down in Tampa, and spent a week in Ft. Lauderdale before heading south to Naples. Wandering round, we were approached by two guys in Hawaii shirts and shorts who demanded to see our ID. When my mate said 'show us yours' they pulled back their shirts to reveal badges and guns on their waistbands. They made it clear we were not welcome in this area, where Liz Taylor and other famous people had homes, and ordered us to leave.
We bought Greyhound tickets and travelled up and across the southern states. In Tallahassee Bus Station, we watched amazed as a crack deal went down in broad daylight in front of us, the buyer paying with a gold chain he had just pulled from a young woman's neck. We continued to New Orleans and partied for a few days before heading into Houston, where we were recommended a hotel called the Montague. Terrific place. The guy behind the reception desk had a tourniquet around his arm, which set alarm bells ringing but it was cheap enough so we paid and went up to our room. Opening the door we were confronted by two single beds, both with what looked like vomit and faeces stains on them. Pulling back the blind we could see rats as big as cats scuttling around in the side alley. The 'peephole' in the door had been removed and plugged with a tampon! We realised this was a big mistake, and got out the room to be confronted by half a dozen big gang -type guys, knives and guns tucked in their belts but clearly on display. 'You checkin' out already?' one said. 'No, just going out for a look round' we replied and carried on walking. Once outside, we bolted to the nearest Days Inn and stayed there for the rest of the night.
The novelty was wearing thin by now. We continued down to San Antonio, visited the Alamo and went across the border at El Paso just so we could say we'd been to Mexico, then made our way back to New Orleans, staying in reputable motels, lesson learnt. We tipped up on Canal Street on New Years Day. The hotel we had stayed in previously was closed down - someone had gone crazy with a gun the day before and mowed down five people. From there it was red-eye bus ride all the way back to Tampa and on a flight home, our pre-conceived romantic notions of the US completely blown to pieces.
I didn't go back to the US for another ten years, when in 2001 we went to NY to celebrate my fortieth birthday. It was marvelous (as long as you like going up things) and we did all the tourist stuff you would expect - helicopter ride over Manhattan, stroll through Central Park, Maceys, Empire State Building and lunch in the Window to the World. Six months later the Twin Towers would be gone, and I consider myself privileged to have been able to enjoy this wonderful city before the necessary security measures brought in after the tragedy precluded many from having the same experience. My point is, this trip would not have been anywhere near as successful (I doubt) had I not learned the lessons of the roadtrip and planned our movements much more carefully and responsibly.
More recently, about five years ago, we did the Disney thing with the kids. We decided to drive up to the Kennedy Space Centre one day. I was advised to have a full tank of fuel and not to make any stops on the way, as it was a notorious road for tourists being robbed at gunpoint.
Don't know what I'm trying to say here really, perhaps just trying to explain how my experiences formed my opinion that America is a dangerous place to go. The rational part of me knows this can't be the same everywhere, and there are for sure places I'd rather not venture in good ol' Blighty, although I wouldn't generally worry about being shot.