I already answered this in the other thread. It’s complicated!

I assume you want an answer with a little more meat on the bones, though. I have thought a bit about the whys, though I don’t really have much insight into the “how we change it” parts. With armchair historian and mass-psychologist mode activated, it comes down to a heady mélange multiple factors:

-a civic religion built around the founders and their writings. There is a notion that if it’s in the constitution, it was a good idea. Christ what I wouldn’t have given for the Second Amendment to have been more tightly drafted for subsequent developments in American grammar.
-to follow on that, our Constitution is basically “Modern Democratic Republic” version 1.0, or maybe 1.27 at this point, but the point remains that their are first mover disadvantages that have us operating with an overly rigid governing document, including a framework that makes it wicked hard to change the damn thing. Good should not be the enemy of the perfect, but when dealing with gun policy, a constitution that is merely “good” has a literal death toll.
-a country born of rebellion against central authority that was previously viewed as completely legitimate has inculcated a culture where armed rebellion is unthinkable… but only for now. The US Civil War and particularly the rapprochement by white elites in the North and South after official “Reconstruction” ended has not helped this one bit.
-a frontier mindset that help may not be coming, even though that is dangerously anachronistic.
-a diverse population that has communities who have been actively oppressed by the powerful, leaving them inclined to retain an option of self-help, and a powerful class that – not illogically – believes that those they’ve oppressed may at some point not be too happy with them. I don’t want to overstate this; I do NOT think the country is on the edge of mass class conflict; I’m just saying it’s one more little half-conscious social pressure.
-a very real segment of the population that believes hunting and agrarian outdoor life are important, either to them as a lifestyle, or as a part of the “proper” American culture.
-a sense of American exceptionalism that if we do something and live in the greatest country on Earth, then changing it to be like the rest of the world necessarily implies that this change must be a weakening of the American spirit in some vague, unformed way.
-a huge number of other issues and priorities that make the political party that is less committed to the gun culture unwilling to spend its political capital on gun issues. As horrifying and preventable as they are, even our huge number of mass shootings still leave the US a fairly safe place to live by global standards.
-last, but not least, various industries and lobbying groups that have a vested interest in pushing narratives that reinforce one or more of the above, with the built-in advantage that they don’t have to get anyone to change anything.

America is a weird country, probably overly large, yet with centuries now of the various sections and communities existing under one government and with many more shared cultural practices than differences. It’s got a uniquely sad subtext to its national story though, where the things people believe make it great are the same things that make it dangerous, and honestly for a lot of reasons, not just guns. There’s a lot that’s quite wonderful about the US, and I don’t think any of that goes away if we rethink some of our sacred cows.