I am from England, something you can't really tell from looking at me but something my accent gives away almost instantly. Although I don't think I sound too different, I have been told otherwise, especially by people who don't spend too much time with me. I have had many troubles during my past two years of living in America and today is the day I give the official guide to my speaking. I start with my first encounter with my roommate when we were both searching for different items through the confusion of the word "flannel."

American to British

Flannel - Plaid Shirt
Washcloth - Flannel
Apartment - Flat
Eggplant - Aubergine
Zucchini - Courgette
Bangs - Fringe
Trash Can - Bin
Cookie - Biscuit
Biscuit - Scone
Sweater - Jumper
Romper - Playsuit
ER - A&E (Accident and Emergency)
Butt - Bum
Call - Ring
Candy - Sweets
Dessert - Pudding (not specific to pudding but applies to all desserts)
Supermarket Cart - Trolley
Fries - Chips
Chips - Crisps
Closet - Wardrobe
Cabinet - Cupboard
Bus (privately rented) - Coach
Cop - Policeman
Overalls - Dungarees
Elevator - Lift
Fall - Autumn
Costume - Fancy Dress
Soccer - Football
Period - Full Stop
Yard - Garden
Gas - Petrol
Vacation - Holiday
Injection or Vaccination - Jab
Jelly - Jam
Gelatin - Jelly
Pinny (Sport) - Bib
Panties - Knickers
Rent - Let
Liquor - Spirits
Popsicle - Lolly
Could you... - Please may you...
Sneakers - Trainers
Ass - Arse
WOW! - Blimey!
Dull (knife) - Blunt
Throw - Bung
Bye - Cheerio
Thank you - Cheers
Chat - Chin Wag
Pleased/Glad - Chuffed
Attractive - Dishy
Man - Bloke
Procrastinate - Faff Around
Two Weeks - Fortnight
Look Around - Gander

I could continue on and on but these are the main day-to-day conversations and confusions British and Americans encounter in their alternative countries. That being said people are always very patient and interested in my use of vocabulary. THANKS FRIENDS! Rule Britannia.