Yes it is the same language.. kind of.
After living in England for the past 8 months I have realized just how many words and phrases are completely different. Here is my quick and dirty list of the most commonly used English words and their "American" counterpart:
School/Sports words:
Rubber (eraser)
Rucksack (backpack)
revision (studying)
prep (homework)
college (associates degree program)
6th form (junior/senior yr in highschool)
diary (calendar or planner)
football (soccer)
Uni (college or university)
A-levels (advanced level courses taken by students last two years of highschool)
GCSE (two year looping courses taken by lower highschool students)
Year 1 (kindergarten)
public school (private school)
state school (public school)
Clothing:
jumper (sweatshirt)
boots (cleats)
trainers (tennis shoes)
trousers (pants)
knickers or pants (underwear)
braces (suspenders)
bum bag (fanny pack)
pullover (sweater)
wellies (rainboots)
Food:
biscuit (cookie)
lolly (popsicle)
pudding (generic word for dessert)
tea (dinner)
dinner (lunch)
cuppa (cup of tea)
banger (sausage)
chips (french fries)
crisps (chips)
coriander (cilantro)
courgette (zucchini)
flapjack (granola bar)
tuck (snacks)
bevvy (alcoholic drink)
jacket potato (baked potato)
Cars/Driving:
bonnet (hood of car)
boot (trunk)
caravan (camping trailer)
dual carriageway (highway)
drink driving (drunk driving)
lorry (semitruck)
trolley (shopping cart)
car park (parking lot)
zebra crossing (crosswalk)
multi-story (car park)
wing (fender)
Everyday terms:
nick (to steal)
creche (nursery or daycare)
hob (cooktop)
bespoke (custom made)
lift (elevator)
do (party)
queue (a line)
lugs (ears)
mate (friend)
till (cash register)
quid (1 buck or dollar)
bits and bobs (odds and ends)
chap (guy)
torch (flashlight)
plaster (band-aid)
Common Phrases:
She's fit (hot)
Fancy someone (like someone)
keen (intent on something)
banter (joking around)
brilliant (awesome)
You alright? (common greeting)
arse (butt)
bloke (man)
buggered (messed up)
well done (good job)
unlucky (bummer)
chuffed (pleased about something)
cheers (thank you)
it's gone off (it's rotten)
Around the house:
toilet or loo (bathroom)
flat (apartment)
let (rent)
garden (yard)
rubbish bin (trash can)
wardrobe (closet)
hoover (vacuum)
cooker (stove)
drawing pins (pushpins or tacks)