The automobile simply shattered these old-fashioned traditions.Dating was removed from the watchful eyes of anxious parents.
For the more technical minded readers, this can be due to Allophilia and is possibly explained by evolution: more dominant genes, and an improved immune system in the offspring.
Compare Foreign Fanservice and, of course, Everything Sounds Sexier in French.
As a result, a larger number of teenagers were thrown into a common space than ever before.
It was only natural that discussions about commonalties would occur.
Certain nationalities are stereotypically presented as inherently "sexier" than others, to those not of that nationality.