1555 In the papal bull Ilius of 1555, the Pope had conferred the title King of Ireland on King Philip II of Spain when he was married to Queen Mary. Philip II made no claim to the kingship of Ireland after Mary's death in 1558.[citation needed] He engaged in a lengthy war from 1585 with her sister Elizabeth I, and he and his successor Philip III supported the Irish Catholic rebels up to the siege of Kinsale in 1601. He had been offered the kingship in 1595 by O'Neill and his allies but turned it down. Given this lengthy support, it was reasonable for O'Donnell and O'Neill to imagine that they might solicit help from Philip III, but Spanish policy was to maintain the recent (1604) Treaty with England (Wikipeadia Aug2024).
Don't forget, when you go back further, alot of Scots actually came from Ireland. So regardless of religion, one could say that quite a few were actually coming home to Ireland from scotland
Seems to me the Ulster Irish brought it on themselves. Only the southern Irish are the natives of this land both south and North, those in the north fled to the south realizing what they had done.