I don't know about Gaelic, but German language and culture in the USA was ruthlessly suppressed during World War 1, and they were forced to assimilate into the broader Anglo culture. I don't see that happening today if 10% of our population speaks Chinese as their primary language & we go to war with China.
Also, German religious leaders tended to promote integration more than Irish religious leaders. Irish Catholics tended to be highly conservative, and were also viewed (rightly or wrongly isn't totally clear) as sympathetic to the South and slavery up until the Civil War, when they fought for the Union of course, but also led draft riots in many cities.
