Ireland is a country with a rich and controversial past, about which, if you want, you can find a lot of references.
English King Henry VIII, when he wanted to get married again, he didn't conspired with the Roman Pope and established his Church of England. And relations between Ireland and England especially have been soured since that time, because Ireland remained Catholic, but England already wasn't Catholic and don't particularly want to tolerate Catholics. From the end of XVII to XVIII century under the pretext of fighting the Catholic conspiracies British authorities issued a series of punitive laws, which deprived the Irish Catholics of political and largely civil rights and established a system of gross national and religious discrimination.
Irish, under such conditions slowly began to emigrate to America.
Discrimination has been continued rather long, until North American War of Independence broke out, but in France - revolution. Against the background of these events, which was backed by their own desire to be free, Ireland has inflamed the national liberation movement.