This is a controversial topic, so discussion should be focused on the scenario and not on OTL Israel or Irish Republicanism.
Basically my scenario is what if a kind of Irish Zionism developed in the 19th Century. They have a big enough diaspora for it and say Nativists come to power in the US...
Let's say that Ceuta turned out to be a disaster, with John of Aviz as well as all his legitimate sons dying. Let's also say that Afonso, 1st Duke of Braganza survives.
There are now three contenders for the throne. John's eldest daughter was Infanta Isabella, who happened to be married to...