Every two-three months, somebody started a topic "females and chess" in the forum here; the last is here. I wrote an article today and submited it at the page 2 of discussion (comment No 30). I publish it here too.
It's enough experiences to say a difference in interest for chess and level of skill between genders is NOT "mostly a cultural issue". You refered to "western countries" - you need to refer also to former comunist countries of Eastern Europe, including former Soviet Union (Russia and others). An equality of genders was one of key issues in comunist's ideology (my parents educated me this way, and equality was a natural presumption for me - I said I am post-feminist 
; males are generaly physicall stronger, but it's not realy important - I am prety tall and strong, I sometimes beat guys in arm-wrestling - and there are extreme differences in physicall and mental abilities within every gender).
Still, statistics say there are differences in some achievements - boys are generally better with numbers, girls with words etc.. So what? It don't means we are not equall in general.
However, in chess, we can look at experiences of former Soviet Union, especially Russia. Governement suported chess strongly, and there are 90 years of experience. Even today, half of best 100 chess players in the world, according to FIDE rating list, are from ex-SU; and maybe half of ALL chess players in the world are from ex-SU. Students leart chess in every elementary school, girls equally as boys. Female chess were strongy suported.
And a result is, still, that before Judith Polgar, except Vera Menchik in 1920s and 39s (she was Russian, living in England), only two women were among the first 100 in the world: Gaprindashvili and Chiburdanidze. Both from Georgia - and female chess in Georgia is an exceptional case!
At the moment, there are 61.603 players on FIDE rating list with rating >2000, and 3779 of them are women - 6% only. Fom Russia: 8423 both, 842 women - 10% only, after 90 years of experience. Georgia is, as I said, an exception: 246 both, 79 females i.e. 32%! (And in last 10-15 years, China too). Still, the best female in Georgia is No 17 at the national rating list - not good enough.
And, let us go back to general numbers. As I said, among players with rating >2000 only 6% are females. And then:
- * >2100 both: 40215 females: 1832 4,6%
- >2200 21025 708 3,4%
- >2300 8229 233 2,8%
- >2400 2898 73 2,5%
- >2500 845 15 1,8%
- >2600 176 2 1,4%
It's very clear: higher level of skils - lower percent of females. If we compare achievement in physical sports, statistics can be very similar, I supose. We can't find even similar difference in intelectual achievements, even mathematics or ingeneering. And as I mentioned before, my friend's remark (female, karate black belt 2nd degree): women are about 20% among karate masters, and about 2% among chess masters. (They must not fight agaist males for black belt, of course, but even if they need, they could win sometimes - as they actually do in treinings and unoficial matches - and at least 2% could take a black belt.)
So, I concluded that difference is so high that you can't explain it only, or mostly, as cultural issue. OK, males are generally better in chess, as like as in karate or aero piloting; so what? I am still among the top 2% here, and I strugle to be among the top 1%. 
And, as I said before: women are about 60% in high education now, and in next decade a percentage of women in top positions in politics, bussines, science etc. will continue to grow. There are more males in physics and more females in biology - so what? I can beat some guys in arm-wrestling, but most of them can beat me - so what, in both cases? I am prety agresive in chess (sometimes in life to, but usually not... err... I think I am not 
), I like to win and I am frustrated when I lost, and I work to improve my skills and results - as everybody else. What is case IN GENERAL is not important for me PERSONALLY.