For whatever reason, it is almost impossible for a Roman Catholic to become POTUS. That is why there has only been one in our history....JFK.
There is a large part of the electorate, especially in the South, who would never vote for a Catholic, period.
Agreed that the prejudice against Catholics is much less than previously in the population as a whole, there are core groups necessary to win an election, the Scots-Irish, for example, who would never for vote for a Catholic.
Read James Webb’s excellent book, “Born Fighting: The History of The Scots Irish in America “. He traces it back to ancient Rome, and it persists today.
The Scotch-Irish were Catholic themselves for a thousand years. Their anti-Catholicism is a product of English divide-and-rule propagandisation.
Having said that, those prejudices do run deep.
Whatever reason? There is a plain and simple reason; this country was founded by Protestants. There is considerable antipathy between the groups historically. Yet in 1960 JFK became the first Catholic president. I find it hard to believe that in the half century since then, the US has gotten more religiously conservative. Folks were saying the same thing about an African-American President a year ago. I think between Blacks and Catholics, the former would suffer more from prejudice than the latter.