Firearms are also widely available in Canada, but the Canadian gun murder rate is eight times lower. Even in countries where assault weapons are widely available (like Switzerland and Israel, where military reservists keep their weapons at home), the firearms-related death rate is less than a third of the American rate, and mass shootings are very rare.
"Violence is as American as cherry pie," as H. Rap Brown once put it, and on the whole Americans have decided to live with it. That's not an entirely unreasonable decision, because changing a whole culture is hard, slow, uncertain work, and 13,286 gun deaths a year (including massacres, one-on-one killings, suicides and accidents) is only one in every 25,000 Americans.
But what about terrorism? That's a real threat, isn't it? The aforesaid Donald Trump even tweeted that President Barack Obama should resign immediately in disgrace if he didn't say the words "radical Islamic terrorism" out loud. But it's not even clear yet if that's what the Orlando horror was really about.
It's true that the Orlando shooter, 29-year-old Omar Mateen, was born in New York to Afghan immigrant parents who raised him as a Muslim, but his ex-wife says that he wasn't very interested in Islam. Maybe he changed after she left (he used to beat her up a lot), but his father says that the trigger for his killing spree was seeing two gay men kissing in public in Miami.
On the other hand, there are reports that he called 911 (the emergency services) to declare his allegiance to Islamic State just before he started shooting, and some witnesses say he shouted "Allahu Akbar" (God is great!) as he was killing people. Even if true, this doesn't mean that Mateen was acting on Islamic State's orders. IS websites do not encourage potential supporters to phone head office for instructions before going out to commit terrorist acts. Just go and do it, that's all.
But it may also be that Mateen was acting out of a so-called "gay panic" - an extreme reaction to displays of gay affection, generally because the person is desperately suppressing such desires in himself. In that case, the whole "Islamic" thing would have been a cover for his real motive, which he wanted to conceal. We'll know more later, but we may never know his motives for certain. It doesn't much matter: people commit massacres for all sorts of bizarre reasons, and it makes no difference to the victims which particular one is driving them.
It shouldn't make much difference to the public or the politicians either, because Mateen is one more mass murderer among hundreds, very few of whom are Muslims. Donald Trump (and some other people) will be pushing the "terrorism" button as hard as they can, in the hope that they can fool people into backing extreme solutions to what is really a very small problem, but that is just cynical self-interest.
So what should happen? Nothing much, really. The US will go on living with the occasional mass murder because the culture is too hard to change, and terrorism - whether this particular event was terrorism or not - will continue to be one of the (relatively minor) costs of doing business in the 21st century.