This seems almost akin to the tragedy of the commons. Society needs for various reasons (e.g., to maintain and promulgate culture, to power welfare and labor needs, to generally exist in the next century) for people to have children at least at some level above replacement rates. However, each individual couple has a lot of disincentive to have children. I am not convinced this disincentive is due to a lack of benefits from the state - I don’t see benefit-rich Western Europe doing much better than the austere United States. I think we as a society and as individuals simply don’t value creating and raising children as one of the most rewarding and important activities to be performed enough to outweigh the financial, social, and personal implications.