You just have to learn and become familiar with them and Canadian and Australian and …………

It all originally comes from German (Anglish as in Anglo Saxon from the Saxony region of Germany) and then from the Roman influence during the Occupation of lower England and the Norman occupation in 1066 that eventually formed the English that we know today.

The two countries split and we formed (the US) from so many different cultural influences that we sorta created our own thing. But bear in mind that there are many, many different accents and dialects within the US and Britain both.

(1) Americans slur their consonants (except they do not drop their Rs and they generally pronounce WH as HW, not just a W, Brits slur their vowels, but although the Americans pronounce unstressed vowels, they do tend to distort the pronunciation of short vowels–American “sorry” sounds to a Brit like “sarry”, and American “pin” sounds to a Brit like “pen”.Spelling pronunciations (lieutenant, clerk), are much commoner in the US. And of course slang is often quite different (grass v. stool, blackleg v, scab), and although US slang is widley understood in the UK the opposite is seldom the case.. (2) There are innumberable vocabulary differences, sometimes due to American conservatism (“gotten,” “herb” with silent h), puritanism (“homely” for “ugly”, the vulgarism for the fundament pronounced with a silent R), love of Latinisms (“principal” for “headteacher”), historical differences (“creek” for “brook,” “store” for “shop”), Hispanisms (“tornado” for “whirlwind”) and a preference for the latter part of long words (a bathtub becomes a bath in UK, a tub in US, a tinned can becomes a tin in UK, can in US, a taxicab becomes taxi in UK, cab in US, a reel of cotton thread becomes cotton in UK, thread in US…), and many technical terms differ (a railway waggon’s bogie becomes a railroad car’s truck. An aircraft undercarriage becomes an airplane landing gear). (3) UK spelling derives from Samuel Johnson’s Dictionary of 1754, US spelling from Noah Webster’s Dictionary of 1811–Sam Johnson’s opposition to US Independence lost him market share. (4) Americans are more conventionally polite, particularly in the use of “Sir” and “Ma’am.” (5) Americans (and British Northerners) do not distinguish “will” from “shall,” keep the short A in dance, castle, can’t etc. (6) Americans are less strict than Brits in distinguishing in usage the past tense (I did) from the present perfect (I have done).