Why do ppl think ethnicity is a euphemism for race?

it has to do with culture not race. race has to do with race. so by this logic the census is wrong. white/Caucasian white is a race but Caucasian is not an ethnicity that would be like Bavarian sicilian parisan those are ethnicities or american.so what about white south africans their race is white but if they come to the usa they are Americans from africa so african american.but ppl think african american is a euphemism for black but what about ppl from libya morocco many arent black but would they be considered african american if they came here ?what about white latinos are do they put white as their race like castro what about black latinos do they put african american if they are born here?but the BIGGER question is why put this on job applications? whats the point.you dont know someones race if they put hispanic or latino they could be black white or mixed or just pure native american like evo morales.and african american can mean someone like Alicia keys who is very mixed or wesley snipes who is pure 100% black.