"You know, I suppose I could have stayed home and baked cookies and had teas, but what I decided to do was fulfill my profession, which I entered before my husband was in public life." (Source.)There was a media backlash and she was forced to bake cookies, claim that she had baked lots of cookies and poured tea a lot in the past. Supposedly, her comments were taken as an affront to women who chose to stay home with children.
However, I have a different theory. I think it has more to do with a reluctance to accept that the United States has a ruling class. We have it in our Declaration of Independence:
"We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty, and the Pursuit of Happiness."(Back then, "men" meant white male landowners, but by now it has evolved to mean all citizens of the United States, more or less.)
We broke away from the British monarchy and the concept that rulers are born.
And yet, with all our talk of equality, and all of our real opportunities for women that many countries don't have, we haven't yet had a woman as president (or even as governor of California, where I live). They have all been the standard white male landowners.
England has had several strong women as heads of state: Elizabeth I, Victoria, Elizabeth II and Margaret Thatcher. Other countries with arguably worse conditions for women in general have had (or do have) women leaders: Pakistan (Benazir Bhutto), India (Indira Ghandi), Chile (Michelle Bachelet), Israel (Golda Meir), Ireland (Mary Robinson), Nicaragua (Violeta Chamorro), The Philippines (Gloria Macapagal-Arroyo), etc.
In many countries outside the United States, the concept of a ruling class or an upper class is more accepted, and women in the ruling class don't need to take care of children (they have nannies), cook (they have cooks) or clean (they have maids). This gives them the possibility of running a country because they don't have to run a household.
Ironically, in the United States with our ethic of equality, we as a nation have a tough time accepting a woman who is not domestic because that would imply she is somehow above the rest of us. We want life to be equally filled with chores for all women! Denial of class structure trumps feminism.
For a woman to have reduced household duties to the point where she can run a country, she needs a staff, and needs to be rich and thus can appear to be in a separate, higher class than the rest of us. A man just needs a wife. (Of course, rich men's wives have lots of help, but it is more hidden from us.)
As the pigs in George Orwell's "Animal Farm" said to justify their control of the government, "All animals are equal, but some animals are more equal than others."
That's the United States in a nutshell, but we don't want to believe it. If a woman becomes president, we would be confronted with that uncomfortable state of affairs, and so far, that discomfort has outweighed our desire for equality between men and women.