I can’t speak for those people. But After dozens and dozens of conversations I think I get it it comesdown to 3 things:
1) Denial
2) Individualism
3) Politics
Denial is self explanatory.
Individualism is more nuanced. I’ll elaborate. In the US a great emphais is placed on the individual this plays out in many many ways. for example healthcare, a broader safety net, duty to rescue laws and gun control.
In all these cases you need to weigh the needs of an individual vs society. My health care is taken care of by my company, I have a job etc etc. Sure it is nice to give charity to someone who doesnt have a job. but that isn’t OUR obligation. Its every man for himself .
In Europe more of an emphasis is placed on the group WE all need to take care of each other we need to ensure the group has access to health care.
If I see someone in danger, in the US the view is sure I should help but that’s if I want to I shouldn’t be obligated to. Thus there is no duty to rescue law (of course there may be a moral duty to rescue that is a separate issue) In many European countries (eg France, Germany, Poland, Portugal, the Netherlands, Italy, Denmark, Russia, Norway, Romania, Turkey, and Hungary) there is suche a duty IF you can rescue someone in danger you MUST do so. you cant choose not to.
This plays out with guns. I won’t kill anybody. so even if we are all better off with stricter gun control , why should I give up MY gun ?
See PEw research study “The American-Western European Values Gap” specificly on Individualism and the Role of the State.
THIS is in my opinion THE main reason. Other arguments falling back on the second amendment, cherry picking data are fluff. The crux of the issue is role of individual vs collective
3) Politics also doesn’t need much elaboration. The NRA focusses on this specific issue both on the political front and on the public perception front. Thus any measure of gun control (even when there is wide public support such as expanding background checks) is politically risky.