One, I forgot to mention the presence of children in the household being a big predictor of the gap. Again, especially if you're rich and white.
Two, no analysis of the census or ACS data can settle the issue of gender oppression. I have no doubt that women are oppressed in the U.S. In many ways, some of them subtler and some of them crasser. But oppression may not be captured simply in the measures of the gender gap. Why not? Because with those data sets (and they are among the best ever/in the world to look into these issues), the division of rights and obligations, resources, etc. within a family or household is a black box. When highly educated women decide to work part time, stay home, spend more time with their children, etc., it's not entirely clear to me that their decision is made under much economic duress. So, I tend to presume that they are are in a better position than, say, poor Black or Hispanic women to negotiate the terms of their conjugal relationship.