The thing is that a society does not always do only ONE thing. You mentioned that there are better ways to protect kids. But maybe they cost more (e.g. banning firearms is dead cheap, while setting up a structure with lots of psychologists specialized in teenager problems is really expensive).
Also you can do one and the other ... at the same time. E.g. suicides of kids/teenagers (<= 19) in Germany in 2025: 216. That is, compared to the population in this age group, 1.38 per 100'000. In the USA that ratio is 9.4 in the age-group 15-19 and 2.3 in the age group 10-14.
And keep in mind, the total deaths by firearms in Germany in 2024 was "just" 168 (we have 1/4th of the US population, in the US police forces alone killed more people ... the total number of 44'000 firearms deaths in USA/2024 is even more staggering). Even if I multiply the 168 by 4 for the population difference ... then 672 vs. 44'000 is still a point of shame for the USA.
So in Germany, we do BOTH better regarding firearms AND regarding health services on kids. And if the USA truly would try MAGA they'd actually copy good results from other countries. So a real-MAGA-person must be against liberal firearms distribution AND for better social health work with teenagers.
BTW, the USA ideology of "the population needs arms to fight a corrupt state" is laughable. When you had your armed religious sects clash with the state, then the state always won. They still have more and better weapons and armor. On the other side, if you look how east-europe shed off their socialist regimes 40 years ago, than nowhere was an armed general population involved. So one can conclude that private firearms may as well be highly regulated and diminshed.