> I can't imagine it's somehow safer in Mexico
It's far less safe in Mexico than in the US, though it's probably still safer in Mexico than Americans perceive it to be in the US.
> just somehow parents are more willing / less informed to take this risk.
You seem to presume Americans are well informed here; they are not. They consistently vastly overestimate the current risk and incorrectly perceive it as increasing when statistics does it is decreasing. Mexicans could be more willing to let their kids out because they are better informed (at least, have a more accurate perception of the risks) rather than less informed.