While I've never written an interracial story with a black heroine and white hero before, I have done an interracial book, OBSIDION: PEARL OF PASSION, in which the hero's Oriental and the heroine white. Of course... it is a futuristic, and the conflict in the story has little if anything to do with cultural differences. I've also written a whole contemporary series (BLACK GOLD) where two of the heroes and one of the heroines are Middle Eastern and their mates are caucasian (some gentile, some Jewish).
When you come down to it, all erotic romances are fantasies about a man (or men) and woman falling in lust, in love, and committing to each other for all time. The racial differences are THERE, but they don't constitute anything more than a descriptive tag and maybe an opportunity for some conflict based on WHO the characters are inside, which of course has been shaped by their upbringing.
I'm not black, Oriental, or Middle Eastern, but I believe I can create believable characters who are, from having observed people of all races and many cultures, in all sorts of situations over more years than I care to think about.
I'm sure Darlene's parents would have been more aghast at her choice of a pro football player from the 'hood than they were with Travis (her late husband), who came from a wholesome rural, but poor and undereducated environment. I didn't make him an urban dude, though, because I had more knowledge (secondhand, admittedly) about the lifestyle of rural blacks in the South. They are upset when they meet Vlad, who's well-educated and well-spoken, only because he is NOT black. (Think the reverse of "Who's Coming To Dinner".)
Here's a question for you: Why is it that many people believe white authors can't write from the perspective of a black heroine, assuming that heroine's not too far afield from the author's own background, when no one seems to question that a black author can write from the head of a white hero?