English people don't pronounce 'R' if it's not the first letter of the word. Many words spelled with -er, or, and -ize/-ization in the US use -re, -our, and -ise/isation in the Commonwealth. meter-metre, color-colour, realise-realize.

Some slang and terms are different. A truck in the US is a lorry in Britain. Fries-chips, goddamn-bloody, fantastic-brilliant.

Americans generally pronounce big words with a hint of simple-man's contempt, for the sake of street-credit. This is true even in the media. Middle class British speak more eloquently than middle class Americans. Basically, American English at all levels of society is a simplified version that is easier for poor immigrants to learn and use. I find British English more stimulating.