It may be an usa thing.. but not sure.
I personally know loads of IR couples in the org. Just to name a few that spontaneously come to my mind
German-ghanaian
German nigerian
Ukrainian palestinian
Nigerian malaysian
Eritrean-australian
Lebanese armenian
Lebanese german
Egyptian australian
Irish (black-) south african.
German pakistani
British turkish
And the list goes on
It seems the common jw belief helps them overcome traditional cultural differences. .