"PRRI: '31.2% of Americans report being raised in a Catholic household, a loss of 10.3%' and highest among all religious denominations."

Yes, a big loss (retention  rate, 66%), owing to so many factors (according to all churches), not least to secularism; but the CC in American history has never had more than 25% of the American population, and, historically, was often way less than that. So historically, it has dropped 3 percentage points (not more, thanks to immigration [7.4%] and conversions [Pew notes, 2.6%]). On the other hand, Protestant churches together used to claim 65% of the US population in the 1950's, but have dropped to 43.9%, owing to the same sociological factors. And even with 5% of the population (ex-Catholics) who have joined mostly conservative Protestant churches (and to a lesser extent, immigrants who have joined Protestant congregations), it has continued to drop drastically. That is the big story (not ups and downs of CC since 1776)!