I've heard that the more often a Catholic attends mass, the more likely said person is a faithful, practicing i.e. "real" Catholic and not just a self-professing "cafeteria" Catholic. I've also seen studies that show only 10% or so of "self-professing" Catholics actually attend mass weekly. Therefore, the number of "real Catholics" in this country is no higher than 7.5 million (i.e. one tenth of the 75 million that you claim), if that fraction is correct.
The exit polls for the last two presidential elections found that, of the most frequently attending religious group (white evangelical Protestants), 25% still voted for Obama. I'll give "real" Catholics the benefit of the doubt on this one, and credit their 7.5 million weekly-attending Catholics with that same voting percent, thus 5.6 million voted for Romney, and 1.9 voted for Obama. I've been told that any Catholic who unrepentantly voted for a pro-abortion politician has latae sententiae excommunicated themselves from the church, so there can only be 5.6 million "real" Catholics out of the weekly attending group. That's just 7.8 percent of the starting number of 75 million.
If I'm right about the "real" number being far smaller than 75 million, one could make the argument that the changing condition of our country is in direct proportion to the reduced number of Catholics therein. On the other hand, a recent thread showed that the United States has the fourth largest population of Catholics in the world (assuming the less discriminating number of 70+ million). If that number has any qualitative meaning, meaning we don't need to discriminate between "real" and "cafeteria", one could make the argument that the changing condition of our country is in direct proportion to the growth of Catholicism therein.
Georgetown University’s CARA Institute finds that about 25% of Catholics attend every week. Gallup finds that about 40% of Catholics attend mass in a given week. I would find either of those reasonable estimates of who I would call “real Catholics.” But by either of these measures, Christians in general are a small minority of the total U.S. population.
There are clse to as many Catholics as all Protestant, Baptist, Anglican, and marginal Christian or non-denominational churches combined (23-25%), but are outnumbered by “other Christians.”
You’re probably thinking that’s crazy, and it is in a way: Non-active Catholics continue to identify as Catholics, but former members of other Christian denominations quit identifying particularly with one denomination. And the majority of Americans no longer identify with any particular sect.
This means if you poll Catholic vs. Non-Catholic, or church-going Catholic vs. church-going Protestant, you’ll get fairly similar results. If, on the other hand poll Catholic vs. Protestant, you’ll find the Catholic vote is significantly further to the left.