I don't think that's fairly explained by more children -> fewer children.
Something else had to have happened.
I'd hazard that on the whole Americans are less tolerant of risk than they were 60 years ago.
As an explanation, I'd tenuously tie it to a decrease in "real world physics" employment (e.g. farming, manufacturing). When 50% of the population works in farming (circa 1870), they have one way of evaluating risk and human capabilities. When that number drops to 2%, it's easy to forget how robust humans are.
Obviously, we're increasingly aware of the risks (usually without any appreciation of the odds). Previously, you heard through close circles. Now, by the time you're a parent, you've heard of hundreds of ways your child might die through news, movies, etc.
I'm a parent of three, and I actively work to minimise risk amongst my kids where I think it's appropriate, but I'm always conscious of when I'm doing it and try to balance it.
Why we (as a whole) respond that way makes sense from what I know about experimental psych.
If news is optimized for clicks / views, negative stories are more engaging, and the availability heuristic is accurate (aka we assign greater importance to things we can immediately recall), then viewing profit-on-engagement news fundamentally reshapes our opinion of the world.
Something else had to have happened.
I'd hazard that on the whole Americans are less tolerant of risk than they were 60 years ago.
As an explanation, I'd tenuously tie it to a decrease in "real world physics" employment (e.g. farming, manufacturing). When 50% of the population works in farming (circa 1870), they have one way of evaluating risk and human capabilities. When that number drops to 2%, it's easy to forget how robust humans are.