Let's not kid ourselves. The ONLY reason the Catholic Church in America are maintaining it's numbers is because of illegal immigration and the fact that the 10's of millions that are here illegally are Catholic.
There are a lot of Catholics in this country...but the number who are cultural Catholics...who never attend mass....who only show up at weddings, funerals, Christmas and Easter...is at an all time high. They identify as Catholic but you would not know it if you checked their schedule.
And THIS is not just a Catholic problem. This is the state of religion in America. ~80% of the country identifies itself as Christian....but they are not. They are cultural Christians...CINOs (Christians in Name Only). They are no more Christian than Obama.
Calling yourself a Christian doesn't make you one...just like calling yourself a woman when your Bruce Jenner doesn't make you a woman. Going to Church or Mass doesn't make you a Christian either, just like going to a doughnut shop doesn't make you a cop (ok...cheap shot).
It’s possible that illegals swell the ranks of the Catholic Church. I’ll not discount that. It’s a viable idea that needs to be fleshed out. However, the birth rate idea is also true. It’s one reason the Islamic states are going to bury Europe.