Perhaps instead, it's because schools (government?) in Russia, India, and China have emphasized Computer Science, and produce higher number of female grads.
Anecdotally, I attended a tiny engineering school in the midwest, and pretty much all the grad students were international students--women from India and China.
Well, from what GP said, it may be attributable to the culture itself:
"a culture difference between groups who are well represented in engineering, and groups which are not."
Which is to equate (or conflate) systemic bias and cultural difference. In other words, it sounds to me like, "it's not systemic bias, prejudice just comes from people doing the things." It's just a simple substitution, because "systemic" refers to a system, not an overarching one, so while we may not be able to ascribe these tendencies in The Technology Sector (or similar large group), systems have subsystems (a la culture vs. subculture), and it may be that those are where bias becomes encoded.