>- free childcare
Where exactly are all the workers going to come from to support this one? There's already a labor shortage, and presumably you want to make sure child-care workers are highly vetted. On top of this, with an aging population, there's a greater need for care workers for seniors, and here there's a lot of problems with these workers abusing the seniors.
>- walkable safe environments, transportation, and regulations that allow children to move around on their own
This would be great, but most Americans don't want this. They sure as hell aren't voting for it, and achieving it would require basically bulldozing most American cities. Americans have built themselves, ever since the end of WWII, a country and infrastructure that's entirely incompatible with the lifestyle you advocate here. I live in Tokyo now, and it's exactly what you're advocating here, but I simply can't imagine America somehow becoming like this in my lifetime. (It's one of the main reasons I came here.)
Anyway, as other posters have noted, other countries have much of what you want here, and their fertility rates are quite poor, worse than the US in fact.
If you really want to get people to have more children, you need to force society back to the "good old days", where women have far fewer rights, divorce is highly stigmatized, being non-religious or non-Christian is highly stigmatized, contraception is generally non-available, women basically can't have jobs except for schoolteachers (and only until they're married) or maids and need to just find a husband and become a SAHM, etc. Just look at the societies with high fertility, but contemporary and historically: they're absolutely horrible for women's rights. High fertility and large families have always been accomplished on the backs of oppressed women (and I'm not sure it was all that great for most men either).