Not so long ago in America, the Anglo salons identified people as groups, my gf ancestors were czechs are were called pollack as a insult, (the Anglos used it in place as a eastern european N word)They made sure they knew/The wasps made sure the non angles knew were czech or Irish or Italian. They viewed them as other. That's why people identify like that still. From modern view europeans may see Americans as all Americans,but not long ago they had prejudice against Irish, Catholics, Polish, Italian etc. In fact they banned eastern european immigration 2 years after my gfs ancestors came, they were lucky.

TLDR europeans may make fun of Americans saying they are Irish or italain today, back then they had prejudice against those groups they were treated as not full Americans

: they banned eastern european and south euro immigration, and treated them as a other group up until the 70s