It doesn't at all. The nation of the USA (and SA), in the not-at-all-distant past, enslaved and systematically oppressed black people. That is a serious stain on their national conscience. For them to turn around and merely undo the laws, and then claim no further responsibility towards blacks who have been left disempowered, undereducated, impoverished and still widely discriminated against, would be a grave injustice.
If you are dis-empowered, under-educated and impoverished, you can help that person based on those measures alone. That is helping them without repeating the mistakes in the past.
Part of your racial nationalism is to assume that all blacks are "disempowered, undereducated, impoverished", whilst all white people are "empowered, well educated and not impoverished". This isn't the case. That is why the AA approach is fundamentally wrong.
But how can you possibly make reparations for the wrongs done to blacks historically?
By helping the people who are in poverty. If they are still historically or currently poor, they will be helped out.
Your argument is that anything the US would try to do to make amends in real terms amounts to anti-white racism.
No it isn't.
For one thing, it assumes all black people feel like hapless victims. I am sure that Kanye West cries himself to sleep at night because Donald Trump took away the affirmative action program.
It also assumes that all black people are one group and think identitcally. What if one black person in the US states that they don't want Donald Trump (as the king of all white people) to apologise for a crime he didn't do? Is that person no longer a real black person?
I have simply stated that you shouldn't (and cannot in the case of the state) discriminate against people based on their race.