Totall OT: Chins on American actresses

When I first saw Reece Witherspoon in "Legally Blonde", my immediate thought was that she was deformed, and I wondered why she would have been cast.
But I've since noticed that protruding chins seem very common amongst American actresses, leading me to wonder whether they reflect an anatomical difference between American Caucasians, and Caucasians in other countries. Or perhaps a cabal of chin-loving directors has taken over US drama production.
What is, or is not, anatomically normal in a population, is purely a matter of statistics, so I'm not suggesting there's anything wrong with these people.
Still, I wonder what others here think, both US and non US.
Sylvia.