Every ancestor I have found, who was born in Ireland, was born in the six counties that comprise Northern Ireland. They have all been Protestant, mostly Presbyterian, or similar "flavor." This leads me to believe they were ancestors of the Scots who were "planted" there by King Henry VIII or one of his successors (though not Catholic Mary I). Irish land was confiscated by the British and colonized by Scots from the lowland areas north of the Scots-English border. These plantations changed the demography of Ireland and created large communities with a British and Protestant identity.
|Counties in Ireland subjected to plantations (1556-1620);|
courtesy of Wikipedia
I believe the partition of the Republic of Ireland and Northern Ireland is largely a result of the settlement patterns of the 16th and 17th centuries.
So it looks like I should not celebrate St Patrick's Day, but instead celebrate the Glorious Twelfth, a Protestant holiday held on July 12th each year, celebrating the Glorious Revolution in 1688 and William of Orange's victory over James II at the Battle of Boyne on 1690.
Pardon me while I go celebrate today. I might be back tomorrow.