He points out that over half of some 40 million people who gave their country of origin as Ireland are actually of Protestant descent. He also points out that many were Ulster Presbyterians, descending from Scotland in the 17th-century:
“To explain this situation attention now focused on the Scots Irish. The first waves of emigrants from Ireland to America in the eighteenth century consisted largely of Ulster Presbyterians, numbering about a quarter of a million people, who were descendants of 17th-century Scottish immigrants to Ireland. Due to their early arrival and thanks to a multiplier factor, it was argued, their descendants made up a major part of those in America with an Irish background.”
The article offers interesting reading and shines a light on the extent of immigration by Protestants, of Scotish origin, from Ireland to America. I recalled when reading the article the story from the Ulster-Scots musical ‘On Eagles Wings’.