Break out non-hispanic Catholics from the Mexican ones. Andrew Greeley, of all people, wrote a book in which he compared Catholics of different ethnic groups. They don’t all bend the same way. It is the Irish Catholics who have always been Democrats, because wheh they came in the 1850s, they moved directly into the camp of the urban machines. The nativists, who opposed them, at first formed the American party but then after it collapsed, joined the Republicans. Many German Catholics, those in the Midwest, trended toward the Republicans. In Illinois, they supported Lincoln, because they opposed slavery. But the Republican party remained anti-immigrant, and anti-Catholic. James G. Blaine, the Republican House Speaker and 1884 candidate for President, is memorized in the “Blaine” Amendment which aimed to limit Catholic participation in public affairs. Consequently, most immigrants joined the Democrat Party. But German Catholics in particular divided their votes, especially in rural and small town communities.
They are Hispanics, not Mexicans, and they have nothing to do with the many generations of liberal Catholic voting, Hispanics only showed up recently.
Catholicism is liberal and creates liberal democrat voters, the thread topic describes part of that historical effort to break America from it's roots and Europeanize it.