I once heard a filmstrip in high school explaining that American English was the ORIGINAL dialect of English. Apparently, they simply carried over the pronounciations as they’d always been. The British Elite, however, felt that the traditional pronounciation sounded too “common” and began making language modifications, and in the end, the unique “British” accent is the result. The tape also said that the cities (such as Boston) where the accents have a British ring today are those with a high number of British sympathizers during the Revolutionary War.
Not likely. As discussed here there is no one British accent. It varies from place to place considerably in England. Also, there is variation over time. Do you think we, modern Americans, sound the same as our founding fathers? I doubt it.
Also Boston did not have more British sympathizers during the Revolutionary War. Boston specificly, and New England more generally, was the center of the Revolution. Per capita it had more patriots than any other part of the country, with the Boston Tea Party and Intolerable Acts and all. The first battles of the Revolution were fought in Massachusetts because of the large numbers of rebels there. The south was where most of the loyalist support during the revolution came from.
Actually, what I heard was that certain accents found in the more remote Appalachias are very close to the original accents brought over from England and Scotland. Apparrently, these people immigrated over, went up into the hills, and were so isolated that they kept their accents.
Filmstrips??? Ahem, just how old are you, anyway? I doubt anyone under 25 knows what those are anymore. 
I have to admit, I spent many hours in junior high watching filmstrips of various sorts, but none espoused this accent theory. I doubt there’s any way to prove it, unless you can find a book on correct English pronunciation published about 500 years ago.
As a general rule, speech patterns in the colonial countries tended to be more conservative that those of their originating countries. This is the for all of the New World.
That said, there is nowhere in this country or any other in this hemisphere where you can here the accents and languages of the mother country at the time of colonization. Languages simply don’t work like that. But what you do get are elements that have survived in various locals through the years.
For instance the ‘a’ in the American pronounciation of ‘fast’. That has survived from colonial times and the Brits were the ones to change. In fact you can see that sound going all the way back to Old English in words like ‘faeder’ (father).
And for those of you lucky enough to here things like “I’m a goin’ to…” that is also a hold over. The original usage was “on going” or “on playing” as in “he is on playing yonder” then that on got shortened to a and we can still see it used today. Though most of us have given that construction up.
Now as far as what’s going on in Appalachia I would reckon there are quite a few of these hold overs in various places but plenty of Scottish influence as well. In fact huge aspects of the ‘southern’ accents can be traced to a Scottish influence.
english in england, as one of you quite rightly said, is so different in various parts of the country, london and liverpool could be 2 different countries. australian english on the other hand is very close to what we speak here in blighty.
we didnt change amercans changed there is evidence of this but its a case of finding it,now wheres me book?
The vocabulary of Aust. English is very different from Brit. English.
The accent is close to the accents in London and the South East (a colleague of mine from London was mistaken for an Australian three times while we were in the USA), but it’s still a million miles from the accents of the Midlands and the North of England.
There is one feature of Australian speech, the rising intonation at the end of a sentence, which does seem to be creeping into the speech of younger English people.