If you think that then I can see how you get confused and befuddled by actual facts.
Importing 10s of millions of Catholics and their offspring would normally have increased the percentage of Catholics, not reduced it.
“”Catholics were 22% of the U.S. adult population in 1948, according to Gallup’s estimates. That percentage rose over the years and reached its high point in the 1970s and 1980s, when the U.S. population was nearly 30% Catholic. In the last several years, Gallup’s estimate of the percentage Catholic has been 22% to 23%.””
And your point? That was 1960 - 50 years ago now. Old enough to have granchildren born in America.
Do they not count as Americans because they aren’t white?