Sheesh! This is why things will not get better!
Over the years the problems with the other items you have mentioned have been recognized and steps taken to reduce the risks to children whilst also accepting that the items have general household utility. Things like child-proof tops on medicines and chemicals, restrictions on selling petrol/gasoline (only dispensed into approved containers); coupled with parental education programmes that raise awareness of dangers and steps that can be taken to protect children. Yes, guns should not be left where children could get hold of them - but that requirement is at odds with the perceived need to have a gun loaded and ready to hand in case "some shit happens".
Even for suicides things are done to reduce the risk. Back in the day you could buy paracetamol in jars of 100 - and suicides could chug a jar. Now they can only be bought in blister packs of 16 (and you are restricted to 2 packs). The limited numbers and blister packs slow people down enough that impulse suicides using paracetamol (and other non-prescription medecines) have been reduced. A determined and committed person can still do it, but someone having a crisis moment has their risk reduced - and it shows up in the numbers.
I said in my original post - the US has a range of problems that all stack up, but guns and the US gun culture are [IMO] part of the problem. The other countries you mention - less so; and they adjust their laws when problems emerge.