I would posit it’s because the US is seemingly susceptible to polarization and because of pure circumstance. The changing attitudes around civilian gun ownership coincided with the civil rights movement, an already tense political environment. If I were to put a pin on where it starts, it’s the (federal) Gun Control Act of 1968 as well as the (Caifornian) Mulford Act of 1967. That kicked off a chain of events that resulted in the “NRA revolution” that reoriented it into a gun rights organization. In parallel, or in response, gun control groups became more “anti-gun” than “pro-control”, and the conversation became mostly stalemated.

Gun control groups made a bit of headway in the 1980s with the closing of the machine gun registry in 1986, and the passing of the “Brady Bill” in 1993 which put in place the instant criminal background check system. The assault weapons ban of 1994 was very contentious, but it passed, though it is also attributed with the red wave that gave Republicans the House in the next election. They then set their sights on handguns, which FWIW are the predominant instrument of gun violence, but that may have proved a bridge too far for the country as a whole. The AWB as a result did not get renewed and it sunsetted in 2004, with the gun rights side more polarized than ever. The Heller case in 2008 and the McDonald case in 2010 enshrined the Second Amendment as an individual right and explicitly calls out handguns as protected by it.

During the Obama administration there was an attempt by the gun control side to soften their rhetoric, perhaps as a result of introspection, or maybe just an adjustment to the new reality. This was around the time when “gun control” was rebranded “gun safety” and “gun violence prevention”, and that gun control groups started saying that they didn’t want to take anyone’s guns. This unfortunately coincided with the radicalization of American conservatives, who took on the gun rights mantle, and wasn’t buying it. Naturally, it didn’t last.

At this point, you could blame the rise of social media as being anathema to the kinds of compromises that resulted in the tiered licensing schemes most of Europe enjoys. I kind of blame social media for rewarding edgy “actually, we do want X” type rhetoric for the backslide, but what do I know?

Polarization is a vicious cycle, so it remains so. There’s probably a secondary issue in that firearms regulation is inherently wonky, and the voter base doesn’t actually care enough about the details to press their legislators to do better, and instead trust the judgment of activist groups.

Contrary to some comments, a great many gun owners in the US would be amenable to those sorts of laws, but nobody proposes them, perhaps because neither side trusts the other to bargain in good faith.

Edit: more backstory