The significant factor was that the US was going to war against Germany. Since German Americans were one of the largest immigrant groups this had a huge impact on them. They were treated badly by Americans. They were forced to fight against their own kind because of the draft. Ireland was a neutral country in WWI so they did not feel any real impulse to be fighting in this war. Many Irish immigrants were completely against this war. They were forced to fight anyway because of the draft. That led to resentment of many Irish.
