likely both. contraceptives next. capitalism and imperialism require a lower caste of workers to turn the gears of the machine--domestic supply of babies needs to be higher for those machines to feast upon.
On that topic, I wonder how much immigration from Latin American countries impacted this?
People who identify as Hispanic are nearing 20% of the US population - and the vast majority of those come from predominately Catholic countries and many see religion as a much more central part of their life and worldview than other Americans.