It really would be weird to think about an ethnic festival for any of the other major white groups in this country. Can't do English because of their complicated relationship with the founding of America (we fought them, after all). Germans? Self-explanatory. Scandinavian? No fun! Italian? Well, maybe ... but we did fight the Axis in World War II, and besides, Italians don't speak English, and are a bit removed from the Anglo-Scots-Irish majority of white people in this country. So it's the Irish by default!