Well, World War I mostly caused problems between the racial and ethnic makeups of the American cities. Yes, it is true that most of the immigrated Americans, such as Mexicans, the Spanish, and even the native indians supported the Americans during the war, but most of the americans still felt a disliking towards many of the new citizens. There were riots, mobs, and even cults were formed. An example would be the KKK, who were involved in more then just lynching negro americans.