"We faced many of those Irish mercenaries in the War of Northern Aggresion,
the ranks of the invaders were filled with many foreigners, from many lands,
while we were true born Americans."
The South had Irish regiments too. My own people were Scots-Irish and fought in the 1st and 10th Tennessee.
Scots-Irish (Orange) is just another way of saying "not Catholic". The discrimination faced by the "Green Irish" had nothing to do with Ireland and everything to do with Religion.
BTW. My mother (the daughter of a Green Irish immigrant) married my father (the son of an Orange Irish immigrant). Naturally, I fight with myself a lot --- and enjoy it. ;~))
Many have confused "Irish" with "Scots-Irish". Both of these groups immigrated from the Island of Ireland but are totally different groups. The "Irish" were Catholic and from the "South" of Ireland where the "Scots-Irish" were from Northern Ireland or "Ulster" and were the descendents of Scots from Scotland and were Protestant (Primarily Presbyterians).
Both groups were "Celts".