Apart from England itself, the primary source of English is the USA.
Almost all the idioms that derive from before the early 17th century came from Britain. Since then the USA has made an increasing contribution to the language. Many US-coined expressions, like 'a miss is as good as a mile' and 'a sledgehammer to crack a nut' are quite old and are used throughout the English-speaking world. Others, like 'blue plate special' and '23 skidoo' haven't travelled far from their US source.
Newly coined words and idioms almost always come from cultures that are confident and outgoing. Throughout the 20th century the USA added as much to English as even the UK itself. Into the 21st century we are seeing more innovation in English coming from India and other Asian countries.
In recent years, Singapore has given us 'killer litter' (rubbish falling from a high building) and 'Chinese helicopter' (a person who speaks little English). India, which has provided many expressions dating from the time of the British Raj, has recently given us 'mother promise' (a promise that you aren't bound to keep) and 'he's eating my brain' (he won't shut up).