Irish people were forced to eat potatoes because they were subjugated by british lords who took everything else they farmed. When the potato "famine" happened, they were actually still producing plenty of other food, just that the British lords didnt care and still forced them to hand it over.

Admittedly this is the extent of my knowledge on the situation, so you should look it up yourself if you want to know more.

The "Joke" at the irish guy in the greentext is actually pretty insensitive and rude, much moreso than asking a german why he didnt order sauerkraut.

Potatoes aren't even native to Ireland.