But most importantly, in order to buy a gun you need to get a license. This means medical check, passing a theory test, passing a psychological test and passing a practical test at the shooting range. It's not trivial at all.
The culture is completely different to US. Everyone is keeping their weapons in a safe. No bedside tables, car glove boxes or other nonsense. I've never heard of a child taking their parents' gun.
Qua guns, teenagers in other countries don't have easy access to concealable firearms. Dad doesn't have one, and you can't waltz into a store around the block to get one.
The Uvalde shooter purchased his weapon a few days prior. Most school shooters do. Anything making that harder helps.
cars?
Guns are exclusively designed to take lives. Would be useless without their ability to effectively kill things, and most humans outside of America don't think it's important for civilians to be armed.