[driftless2]

This might explain why there are so many different regional accents in Britain. America has about four or five basic accent. Britain, a much smaller country with about one fifth of the population of the U.S., has about thirty or more distinctly different accents. That’s not counting the Scottish dialect either.

[RayChuang88]

Maybe it's an issue with the people in the British Isles not willing to move around the country? Remember, modern transportation is erasing a lot of the regional accents in the USA, and Japan--at least among the younger generation--has far fewer dialects than in the past, thanks to much of Japan now accessible easily via the Shinkansen high-speed rail system.

[Alas Babylon!]

Yet among the 13 original colonies, the majority of people came from that various British stock. There is a book called Albion's Seed, that shows how specific regions of America were settled by different regions of Britain, and how that affected so much, from accents, words used, religion, politics and foods that families ate.

From the review on Amazon:

This cultural history explains the European settlement of the United States as voluntary migrations from four English cultural centers. Families of zealous, literate Puritan yeomen and artisans from urbanized East Anglia established a religious community in Massachusetts (1629-40); royalist cavaliers headed by Sir William Berkeley and young, male indentured servants from the south and west of England built a highly stratified agrarian way of life in Virginia (1640-70); egalitarian Quakers of modest social standing from the North Midlands resettled in the Delaware Valley and promoted a social pluralism (1675-1715); and, in by far the largest migration (1717-75), poor borderland families of English, Scots, and Irish fled a violent environment to seek a better life in a similarly uncertain American backcountry. These four cultures, reflected in regional patterns of language, architecture, literacy, dress, sport, social structure, religious beliefs, and familial ways, persisted in the American settlements. The final chapter shows the significance of these regional cultures for American history up to the present. Insightful, fresh, interesting, and well-written, this synthesis of traditional and more current historical scholarship provides a model for interpretations of the American character. Subsequent volumes of this promised multivolume work will be eagerly awaited. Highly recommended for the general reader and the scholar.

[ThanhPhero]

Louisiana has half a dozen, probably more, distinct accents all by itself, though at least three, maybe four, are accents of French or Creole French/English.

[piasa]

Cajun
N’Awlins
Ozark-Missourah
Missourillini
Southern
Virginian
Florida Cracker
Florida-Cuban
Texan
Californian
Michigander
Wisconsin cheesehead
New Joisey
New Yawk City
New England/Upstate New York
Baahston
Chitcahgo
Ebonics
Jive
Spanglish
Hawaiian
Alaskan
All quite distinctive.

Not to mention a whole bunch of Indian languages...