If you don't shield them from simple dangers they cannot understand, then that is exactly what you may deprive them of. A two year old is not ready to contend with rattlesnakes, mountain lions, electrical sockets, etc.
Danger needs to scale with a child's ability to handle it, and which is likely higher than the average American parents' tolerance.
A two-year-old isn't ready to contend with rattlesnakes. A sixteen-year-old absolutely is. Somewhere in that timeline, there's a stair-step in the danger function, and that's just part of life.
Safety-obsessed Americans would ensure that the rattlesnake stays behind glass forver.