American English is commonly accepted to be a dialect of the English language, and while people from Britain and America can nearly always understand each other, the exact words used do differ from one nation to another.
So going on vacation becomes going on holiday, rather than living in an apartment, you live in a flat, opening a checking account becomes opening a current account, a car’s hood becomes a bonnet and then there are of course all the words that change from containing a ‘z’ (zee) to an ’s’ (most certainly not a zed), er becomes re, and superfluous ‘u’s are also often dropped in American English.