This chart explains why men prefer to meet women overseas. This is not the ENTIRE list of reasons but it gives a hint.
Women overseas have realistic expectations. Single mothers aren't trying to get a 8000 ft² house with 2 cars and be stay at home wives. Their expectations of male interactions with women and what a man wants from a woman are realistic.
She knows what you want and won't play games using it as a carrot. Where as american women play all types of games because they have an embargo on sex. Traveling breaks that sexual embargo and makes it so that American women have to be competitive in an open marlet now.
These women are not wives. They are not wife material but expect a traditional husband.
A big part of PUA tactics involves approaching women. This is arguably one of the most difficult and awkward parts in American society. Especially when we have a culture of women who make it difficult for men to approach them on purpose.
PUA teach you ever evolving tactics on how to overcome these barriers women put up in the west. As soon as women get wind of the tech, they move the goal posts. The game is so advamced that many guys just entering the dating scene after years of productive labor and education/training don't have the time to get into the trenches and fight a meaningless war.
When men travel overseas the approach is completely taken out the picture or drastically reduced. In Brazil for example, women have a custom of approaching men first. Then the man speaks to the woman and they proceed from there.
2 of the biggest obstacles in the west are removed abroad. This is why some men go abroad.