Nice hypothesis.
How do you explain that this happens exclusively in developed countries?
Because women have less power in developing countries, most of them are at the stage where the usa was around the late 50s, early 60s.They find a looksmatched man young, and marry, start a family.Women still are seen as the weaker sex, the man still gets the higher paying jobs etc etc.I know though that this is starting to change rapidly, attractive women from these countries are getting mobile phones, getting instagram, and men from all over the world are starting to message them.Gone are the days where say you could go to Colombia or the Phillipines and have the white man god thing happen.Their attitudes are rapidly becoming more westernised.When women get power, and they do not need a man for resources, they tend to focus far more on looks.