I think both people from the US aswell as people from the UK do not get exposed much to "the other" english. I have noticed it a lot. That one or the other group havent heard of things which even for me as a non-english speaker feel like common knowledge. I guess your own cultures produce enough that you don't need to see stuff from other people :P Plus maybe a bit of pride? We dont need UK/US stuff, we allready got our US/UK stuff.
Over here we sort of get exposed equally to UK and US stuff. Movies are more from the US quizshows and murder mysteries are from the UK , (ow and antique and nature, ow wait that is the on BBC itself, we cant get any american channels though) There arent too many on, but I think sitcoms were more from the US aswell (though that was more the case in the 90s)
But yea vertexen sounds really weird.
Btw I looked up the etymology of callowness, and apparently it is related to the dutch kaal, meaning bald, and callowness refers to be as naked as a babybird, new to life.