There exist dominating languages in western culture - English, Spanish, French, German, and native speakers are getting comparatively easy pass. English has the magnifying factor of mostly American movie and music industries. I mean more the ruthless evolutional and statistical factors - no American, Spanish, French, German lady comes over here looking for romance, marriage, or sex. I might relocate there but starting my life from scratch, I will not be attractive in comparison with more established guys. For a lady starting from the scratch is not much a hinderance, she will find a patron of some kind. So there is natural migration of people and people are free to make their romantic choices, but this migration is very unidirectional and causing significant frustrations among a spectrum of demographics.
Dunno, their perceived higher status and an intention to marry up? Oikophobia based on real experiences (poverty, economic instability) but as well on some imaginary grounds (biased content by mostly foreign owned media, ads)? Probably more and it's more complicated...
because your fellow (female) nationals choose to have sex with Americans? Is America responsible for these choices?
Are "unaware partners" getting just porn? Should women not get to choose who they have sex with before marriage?