In the English city I live in, 'white trash' is occasionally used to refer to young white women who are single parents of biracial children. Typically, it is assumed that the girl in question slept with a Black or Asian (Indian or Pakistani) man, fell pregnant and was promptly abandoned by the father. Racist white eople use this to warn their daughters against becoming involved in interracial relationships, just as they warn their sons that becoming involved with Black or Brown girls will almost certainly get them knifed. You don't hear it as much as you used to.