Acclimation...

This is a fascinating wikipedia entry on the differences between British and American English.  It's strange, I read so many British books as a kid, that I use some British grammatical rules without realizing it.  Sadly, I think spell-checking programs are solidifying the differences between British and American spelling, especially when doubling consonants in front of a suffix with a vowel.  For example, I still write travelling, but most spellchecking programs tell me that traveling is the correct spelling, which looks totally wrong to me.  (Wikipedia also has an interesting article on the different spelling conventions of the two countries.)

Mostly, it gets difficult to remember which conventions to use where, especially when writing for a British audience, as I am when I work over here.  When I bring some of these conventions and colloquialisms back to the US, people think I'm being smarmy or hoity-toity, which is usually not the case at all.  Saying 'cheers' becomes second-nature here, as does asking where the 'loo' or 'toilet' is.  If you're looking for zucchini, you'd better look for a corgette instead, or you probably will go home empty-handed.  And if you want something 'to go,' you'd better ask for 'take away.'  I could go on and on about the subtle changes between American and British English.  It takes a me a few weeks to acclimate myself once I'm over here.