We can look back at the European catholic and protestant wars, where many European countries cleansed the protestants, or the Spanish Inquisition, but in both cases their numbers were never as big, the protestants where a new movement deemed traitors, so it was easier to rile up people against them, for muslims in Spain they were essentially foreigners from a newly reconquered land, not people who’ve been living together for decades or centuries and gotten used to each other, finally people are more motivated by religious fervor than a racial one.
>what about Jews in Germany
The Nazis systematically removed themselves without consulting the white Germans, in your case the state is protecting those non-whites and nothing short of dismantling the state will get you anywhere close of getting rid of them
>is it really 100% hopeless?
No, but the only realistic outcome, is building small new white states, and then slowly expands by conquering the former lands, systematically removing the undesirables. But what you will have by then, is no longer the old state but something entirely new claiming to be vaguely it. Just like HRE claiming to be Romans.