It is company policy to have an Yank SO on board for all the American trips. It's for safety reasons, they're the only ones who can translate such "standard" American ATC phrases as
"triple nickle eight ball come to 23 out of 34 and slow to a buck fifty...".
Ohh, and they can translate "jive" for you when you go out on the town.. Know what I'm saying DAWG!