Hmmm... since this is being read, the biggest difference -- accent -- goes away. I'm not sure I can point you to any specific things that Americans say that non-Americans don't. It's more along the lines of the words they use...elevator instead of lift, hood instead of bonnet, and so on.
In fact, if I were to think of a good source, I'd look for a dictionary that cross-references American to British terms. I had a Chilton's manual for one of my cars that had that in the back of the guide -- wrench for spanner, things like that.
That's probably a good place to start. Next, I'd avoid country-specific phrases. Things like bloke, lad, crisps, bangers, vegemite, and so on. How to figure those out, however... perhaps websites... try
this google search for some interesting ideas.
If you want, feel free to pass it by me and I'll give a review (unless you're really writing War and Peace, Second Edition [img]smile.gif[/img] ).
Good luck!