Why are American boys much more likely to see a future in science than American girls?

The New York Times reported an international test that compared many nations on a test of math and science. In some nations, boys did better than girls—most of these were western nations. In many other nations, girls did better than boys—most of these were Asian and Arabic and Slavic nations.

The article says it is cultural differences that account for these differences. In nations like the United States, the cultural message is that math and science is not for girls, even though they can do just as well at it.

What explains the cultural messages being sent to boys and girls in these different nations? What is the consequence of these cultural messages (notice how US scores, overall, are so much lower than most other Western nations). What can be done about this? What, if anything, should be done about it?