This is a fascinating historical topic to me, since a large share of my maternal ancestry is Irish Catholic ( i.e. 19th century immigrants who settled near Boston and in Chicago), and so I wonder how the meaning of "Irish" or "Irish-American" changed over time, as those Americans of Irish Protestant (or even "White Anglo-Saxon" Protestant in general) ancestry were becoming outnumbered - at least, in certain regions of the country - by poor, under-educated, un-assimilated, and Catholic Irish immigrants by the mid/late 19th century.

When did Irish Protestants/their descendants in the U.S. begin to see themselves as "American", and what role - if any - did the massive immigration of Irish Catholics during the 19th century play in this mediation and transformation of identity for this demographic group?

Furthermore, as my thread title indicates, did Irish (ancestry) Protestants feel especially threatened by Catholic immigrants, or was nativist sentiment toward said Catholics broadly similar to nativism among American Protestantism in general during that era?

Finally, my understanding is that the Catholic-Protestant divide among Irish immigrants (and their descendants) was even more of an issue in Canada than it was in the U.S. (IIRC, the Orange Orders were much more numerous up there - someone can correct me if I am mistaken on this).

Any answers would be greatly appreciated. Thank you in advance!