@meka no one is calling those Irish-Americans, Black. they clearly had white skin and were not Black and did not have Black ancestors. they simply weren't admitted to the "white people" club because they were discriminated against for being uncouth, rude Irish people.
i don't know what you mean by a "US definition of race", but what i'm talking about is pretty much accepted everywhere, not just in the US. if anything, the US is slow to accept this because it means they'd have to confront their history of racism and the social construction of Whiteness that they pioneered.
@meka "white people" are people who are permitted to be white. does that sound absurd? it should do, because it is absurd. Irish-Americans were not considered white because, basically, they weren't WASPs. they were Catholic, they didn't fit in, they had their own communities. they didn't suit the white people club, so they weren't white.
again, if that sounds absurd, yes, it is. racism is absurd.