My international observations completely reaffirm this. Let's consider the differences in just the Arabic world.

I have spent considerable time in Kuwait. It is interesting to see many women continuing to wear the niqab that so many western societies find repressive and possibly sexist opposed to the more western accepted hijab. This garment is not forced by society or law, but is typically a choice of the head of household and the person themselves. I can tell you from my own observations with the wealth and freedoms available women absolutely do not appear strongly repressed in Kuwait and there also does not appear to be ambitious career goals among many (certainly not all) women in Kuwait. Compared to Americans Kuwaitis are lavishly wealthy.

Contrast that with Kuwait's southern neighbor Saudi Arabia where my mother-in-law has been more than once on business. Women were given the right to drive themselves for the first time only about 6 months ago, and the niqab garment is absolutely not a choice. Compared to Kuwait and much of the rest of the world women are heavily repressed in general freedoms. Despite all the limits there appeared a very strong effort of women to wanting to join the work force and take on ambitious careers. Compared to Americans the average Saudi is in a similar place economically, but I suspect the difference is observable societal pressures cause Saudi women to more frequently question their independence and work ethic compared to US women.

What I gather from those observations is that when you have anything you want and almost no performance pressures you simply won't have the motivation to work towards ambitious objectives. On the other hand when societal pressure to perform and compete is high a person is heavily motivated to work towards ambitious objectives.

Kuwait and Saudi Arabia make for good extreme examples, but I would say the stated conclusions apply universally. The US is still so far away from achieving gender parity.

In the US many women do not feel pressured to invest in career ambitions when conservative traditional social pressures say they can marry a man who does feel so pressured and still enjoy median financial results. The important thing about that statement is that it isn't claiming anything about a willingness to work, but is merely talking about investment in a future career. This thinking is largely to blame for far fewer women entering advanced careers of an abstract nature and why in many locales many women are more eager to take on menial work compared to males.

Another interesting observation is the US military. Women are a minority population in the military, but compared to US culture at large the military is generations ahead in achieving gender parity with regards to compensation, opportunities, and so forth. Pay in the military is based upon rank and years of service where subjective qualities have no influence. In about the past year and half the military eliminated its final restrictions upon women entering elite combat training. Promotions are more objective in the military compared to the corporate world (I am a military officer in the reserves and a senior developer at a fortune 50 company).

What makes the US military interesting to observe is performance of women compared to men in the force generally given that women are a minority population. My personal observation is that given a more challenging opportunity and sufficient preparation women tend to fail substantially less compared to males as ratio of sex to total population. In other words once societal pressures are normalized for individual pressures of success/failure take over and individual pressures are high given that there is already an investment in a career.