The guns / access to guns debate is on a level with the chicken / egg debate, except the second is easily answered.
It's the combination of access to guns, and the ongoing gun culture that makes this problem insurmountable.
Republicans like President Trump can entirely embrace the gun culture because it chimes perfectly with his voting demographic. Democrats like President Obama can make a few noises in their last term, but nothing too much because it is easy capital for the Republicans to beat them with.
Nothing will ever change until the frontier mentality that afflicts so many millions of Americans is bred out of them, and that shows no sign of being even close.