Suppose British authorities caught on earlier the rebellion never is but it's enough for Ireland's home rule to not be pushed through, we shall not bend to the will of terrorist, something like that, Ireland truges through WW1 unhappy but maybe gets some level of autonomy granted through a Belfast assembly not based out of Dublin, WW2 breaks out the Nazis bomb the shit out of Ireland too greater feelings of unity come Ireland's countryside becomes a haven for British children, the fifties, sixties, religion becomes less and less paramount in society, today Ireland is just another part of the UK, not anymore unhappy about it than the Welsh.