>78

Actually, diversity in English accents is far greater in the United Kingdom.
In the UK, it is possible to guess the accent of someone from 10 miles away while it takes a far greater distance to do that in America.
Moreover, even within America, diversity in dialects decreases the further west you go.

An example of linguistic diversity in the UK:

http://static5.businessinsider.com/image/575bfcb5dd0895d8018b47f7-1200/here-is-a-look-at-how-varied-our-dialect-was-60-years-ago-this-map-shows-all-the-different-words-our-grandparents-used-to-describe-a-splinter.jpg


And America:

http://aschmann.net/AmEng/index_collection/AmericanEnglishDialects.png