There is a nice bunch of people on Booman doing it too.  (From the Americas as well as Europe)

I think you might have trouble getting noticed because of the sheer number of diaries on Kos, but I've never seen anyone go after someone because they are European.  Like, ever.

Of course, if you go there expecting Americans to be rude and exceptionalist it will probably be reflected in your writing and we Americans have a pretty good radar for detecting that.  

Those who can make you believe absurdities can make you commit atrocities. -Voltaire