How about this:

Yes, 51% of U.S. citizens are female, but they don't all necessarily vote. Also politicians and corporations may pander to voting blocks during elections, but have a bad habit of ignoring those blocks once elections. And, of course, the banks and corporations really don't give a crap about how many women there are (I'm not even sure they've given a crap about voters or citizens at all, ever). I would bet that a little searching will also find some laws that favor men, especially on the state level, but I'm too lazy to look myself.

So yes, if the U.S. were a perfectly functioning democracy with a 100% voter response rate and a private sector that cared, then the patriarchy would by definition be dead. Actually, a patriarchy, by definition, would have ceased to exist in 1920. But ours is not a perfectly functioning democracy, and voter turnout is around 50% in a good year, so, all definitions aside, the men are still hanging on to their power.