Based on conversations I've had with Americans on other forums, I think (amateur sociology coming!) a lot of it comes down to the US coming from a civil war background, which is something Australia doesn't have. I've had friends on other forums talk about why they don't want their government taking guns from them, about powerlessness and how they're uncomfortable with having an armed government and an unarmed populace. I don't pretend to know much about the American Civil War but...is that division still a thing, on some level? And this is all technically true admittedly, I mean maybe one day that will be a problem for us, but we've also never in Australia experienced a government we needed to defend ourselves from, or a division that wide.
More complex though I think is there's a bit of a Pandora's Box effect with guns for two reasons.
Firstly, I think the gun laws in Australia were only controversial for about a minute because it's easier to tell someone you can't have something, that to take something off someone, if that makes sense. Silly metaphor: if I don't have any donuts and someone bans me from having donuts, I've only lost a possibility, but if I have donuts then I'm actually losing something, it hurts more. So yeah it's easier to institute bans of some measure before the fact, but after the fact gets tricky.
Secondly, I believe our gun crime is quite low - when it does happen it's often within criminal ranks, a la the Melbourne gangland shootings - so a self-defence argument over here doesn't go down so well, it doesn't seem as relevant. Certainly I've never in my lifetime had a friend who owned a gun. All that sort of stuff has a murky chicken and egg relationship though.
So yeah I've never gotten on a high horse about this sort of thing because a) I think we were very lucky to have caught it early; and b) even with our western similarities, I think our situations and histories are quite different.
By the way: most interesting thread ever!