"Galpin investigated the percent of women in computer classes all around the world. Her number of 26% for the US is slightly higher than I usually hear, probably because it’s older (the percent women in computing has actually gone down over time!). The least sexist countries I can think of – Sweden, New Zealand, Canada, etc – all have somewhere around the same number (30%, 20%, and 24%, respectively). The most sexist countries do extremely well on this metric! The highest numbers on the chart are all from non-Western, non-First-World countries that do middling-to-poor on the Gender Development Index: Thailand with 55%, Guyana with 54%, Malaysia with 51%, Iran with 41%, Zimbabwe with 41%, and Mexico with 39%. Needless to say, Zimbabwe is not exactly famous for its deep commitment to gender equality."
Source: http://slatestarcodex.com/2017/08/07/contra-grant-on-exagger...
I don't think it's clear why both of these occur however and I haven't been convinced that people who try to derive a position solely off societal level trends tend to do anything other than show off their ideological preference on both ends of the debate.
Places where women also have less choice / self-determination. When women get to choose their career path, they do not choose tech. That is the relevant correlation suggested as a cause.
The "young males prefer trucks, young females prefer dolls" split is also found in chimps FWIW.
Interest drives practice and practice drives skill.