My view personally is that the western media makes women believe those jobs are not right. Women are constantly told men are sexist and indirectly when they enter a male-dominated field I think lots of women subconsciously believe they will face sexism, regardless of their beliefs being ground in reality or not.
Also, I think U.S. divorce laws create a huge moral hazard for women in STEM careers. STEM fields tend to be very difficult and I think lots of women in the back of their mind know that if they fail they will likely have a guy to rely on (maybe not Brad Pitt but even fat and ugly women can still find some dude to support them). However, in most Asian countries, divorce oftentimes is not a life-time gravy train like here. (Singapore is somewhat of an exception).
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Asian girls from what I have seen are very driven and motivated. From what I have seen as a pure science major a lot of the females are from middle eastern and Asian countries. Good on them. I can't quite put my finger as to why its dominantly foreign women in these fields. Very strange. I will keep an eye on this question to see other answers. A lot of my female counterparts in science opted for the more broad sciences like conservation, ecology and psycology where all my male friends tended to go to physics, chem, math, engineering. My friends engineering and physics class is about 95 percent male (a sausage fest as he puts it). It seems to me a lot of girls are just not plain interested in math and phyisics concepts for the joy of it. Males tend to enjoy that stuff a lot more.