your lack of free healthcare, lack of effective welfare, teaching the citizens the only way to happiness is prosperity, picking on other people via the media and calling them the enemy (divide and conquer) is all a factor. There is a lot of supernatural interference in the USA, even for a nation with easy access to weapons, these mass shootings seem awful common.
We don't have a lack of healthcare. This is the age of the Computer mate, we can look up what's wrong in your country of Australia and rail against that. But that would be stupid because we don't live there.
Mass shootings aren't caused by guns being available in America. Mass shootings are caused by mentally diseased people who feel like taking their whatever the hell is wrong with them, out on innocent unarmed people.
Notice mass shooters don't open fire in a police station? They don't go to a gun range and try to throw down. They go somewhere where their attack on unarmed people can tally the most bodies. But if they met armed resistance they'd be stopped before they could put dozens of people in body bags.
And those killers that were stopped by armed citizens don't garner as much media attention as the killers who murder unarmed people.
And don't let it escape your memory. The greatest death toll on domestic soil happened September 11th, 2001. And those psycho's used airplanes as their weapons.
It isn't the gun that's the problem, it's the person who pulls the trigger that is the problem. If we didn't have guns , if they'd not been invented, we'd be in a real fix. Likely speaking the Queen's English still. Or worse.
Anything can be made into a weapon. Years ago a nut decided to use a van as a weapon and mow down joggers in a park. Do we ban vans?
A fork can kill someone. Should we ban forks?
There was an episode on a subway as I recall. A few years ago now some nut on a train started attacking people with a knife. All those people and one crazy with a blade, and the crazy tallied a lot of people as their victims before it all came to an end.
There's no law that can ever be passed that saves the world from crazy.