To focus way too deeply on just the ireland bit:

Ireland (the island) is presently separated into Ireland (the country) and Northern Ireland (part of the UK). This was the compromise made in the early 1900s after repeated attempts to throw off British occupation of Ireland, and except for some changes to the governance of Northern Ireland, that split arrangement also survived the Troubles (a period of violent resistance against British occupation of NI by the IRA and other related groups in the 1970s), but the unification of all of Ireland (the island) into one country, free of British rule and interference, remains a strong desire for many Irish people.

Star Trek had an episode where Data referenced the "Irish Unification of 2024" as a case where violence/terrorism was used to effect positive political change. Basically implying that a resumption of "terrorist" activity a-la the Troubles had resulted in finally achieving Irish unification. Link: https://www.youtube.com/watch?v=IbSGp4WIBsQ

It's also popular here in part because Picard disparagingly references a Mao quote before getting several counter-examples thrown in his face by Data

there's currently a small internet conspiracy that Kate Middleton is missing. prince harry is "in exile" in the US for marrying a commoner. king charles has cancer and has in the past been known to subscribe to herbal remedies over modern medicine. this makes the english monarchy look particularly unstable, which would make it a great time for the French to invade, like the Frankish kingdom has done before. and of course, in star trek tng it is canon that the part of the uk currently known as northern ireland reunified with the republic of ireland in 2024.

The 1300s reference is talking about the first Hundred Year War between France and England. A period where the two were essentially in a permanent state of warfare invading one another at every opportunity.

The Irish stuff is because Ireland is still divided to this day with a piece of it being ruled by the United Kingdom. The Troubles and the IRA were all about freeing Ireland from English rule. People are still trying to free it to this day.

Star Trek lore states that Ireland fully reunified in 2024.

the UK is oppressing Ireland's historic right to to use modulo 31 arithmetic

If you ever heard the argument that “white people were slaves too,” it’s correct. Irish people were slaves to the British. And I mean they’re still colonized now. But the people who like to make that argument tend to leave out the part that, like other slaves of the world, the Irish fought back violently and became notorious and feared by the colonizers.

It's not history it's right now