Show me evidence of this, any at all, and I'll give your ideas more consideration, but otherwise I simply cannot.
In my high school, there was a girl running for class president. Her opponent posted messages on facebook, saying: "Do you really want someone who bleeds once a month in office?" When I told a male friend about this, they simply said: "Well, he does have a point, you know." He wasn't making a joke. He actually meant it.
I have had professors tell me, in math class, as I did work in my head: "What, do you think computation isn't women's work?"
The Berkeley math department has no women's restrooms on some of the floors. Every floor has a men's restroom.
I have never had a female math TA.
I have never had a female math professor.
In my martial arts class, I have heard other women be called "stupid lazy bitches" because they did not move fast enough. I have never heard a man be referred to in this way, or equivalent, when he performs the same actions. A woman who does not perform is insulted in her character. A man who does not perform is told to straighten up and get his ass in gear, because he is a disgrace to the dojo.
I do not remember seeing men hit as punishment during their training. I was. I took martial arts from the same people for two years. I came back four years later and they were still acting the same way.
In the same dojo, I was used to mock the rest of the students because I was small, and female, and I still fought harder than they did.
I grew up with my (male) cousins actively making fun of women as weaker, stupider, more flaky people.
In my entire childhood, I only found two authors who presented strong, realistic female characters. Only one of those authors used a female protagonist. I'll note that I read books for perhaps 12 hours a day, from the ages of 5 through 13.
The Bechdel test exists and I hardly ever find a work that passes it.
That's just what comes to mind after thinking for a few seconds. I live in California.
You want to talk about women losing opportunity?
In an experiment proving
the existence of stereotype threat, women who had to write that they were women performed far worse on exams than women who didn't. Those who perform badly on standardized tests--like the AP tests and SAT--lose opportunity.
There you go.