> A counter is that other countries (Japan, Korea, Italy, ...) that enforce traditional values have had a collapse in the birth rate.

Yes, but the value systems (at least in Asia) are quite different than even conservative ones in the US so I don't think that's a fair comparison. In Asia there is an expectation that relationships will lead to marriage, that you will marry well before thirty, that women will exit the workforce following marriage, that married couples will have children quickly, and that enormous amounts of resources will be spent on raising those children (especially in terms of education).

The birth rate has gone down there because it is overly burdensome to be married and have children under these expectations. This is far different than even conservative expectations in the US which basically amount to the father should be able to hold down a job and show up.