Catholics certainly were having more kids than Protestants at the time, who had by then been normalizing contraception (following the Lambeth Conference of 1930). But eventually Catholics drank the Koolaid like everyone else, so it's less about "cultural confidence" and more about "cultural detox".
Catholics are the only world religious group that rejected the pill. Currently, actual Catholics (who believe and practice the defining doctrine) are the only group above replacement rate.
Cultural Catholics in the United States mostly aligned with Protestant secular world views.
> Catholics are the only world religious group that rejected the pill.
Or rather, the Church has steadfastly refused to sacrifice moral principle to drift downstream along with everyone else. Sure. And it never will go along. But a good fraction of the Catholic laity has.
> actual Catholics (who believe and practice the defining doctrine) are the only group above replacement
With all those qualifiers, the point becomes comical. Obviously, Catholics who actually live in accord with sexual ethics will have above replacement fertility. But a good fraction of those still in the pews are not procreating at above replacement, at least in the developed world. Many use contraception.
