Southern American english varies widely in difficulty to comprehend. The deep south accents (Alabama, Georgia, Mississippi) are more difficult for me to understand when people speak. Then again, I live in Texas, so I am exposed to horrible drawling all the time (though my accent is not very obvious, as verified by third parties
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).
The nature of the southern accent is difficult to explain. It is characterized by slow speech which distorts some syllables and avoidance of sharp pronunciation. Sounds normally pronounced on the tip of the tongue in standard American english are usually avoided unless they begin a word. Examples:
gowyn => going
pardner => partner (the "t" sound has been softened by replacement with "d")
Vowels (especially long "a" and "ou") are sometimes pronounced through the nose.
Northern accents vary greatly, even from state to state. And although I'm exposed to them at work, I'm hardly qualified to quantify their rules.
![Smile [:)]](/emoticons/emotion-1.gif)
Maybe someone else can make a stab at it.
By the way, you are correct in that speakers like the President take great pains to moderate their speech. Bush still has a strong southern accent to my ear, which, unfortunately, is associated in the lay public with poor education. And while you may disagree strongly with some of his policies, as I do, he's no idiot.
I would group the major english American accents thusly:
SOUTHWESTERN: Texas, Arizona, New Mexico
SPANISH: everywhere!
WEST COAST: California, Oregon. Probably closest to "standard" American accent, although Californians have several different accents depending on location
MIDWESTERN: from Montana east to the great lakes, including Ohio, Michigan, Illinois, and Indiana (watch the movie "Fargo" for this one! William H. Macy is one of my favorite actors...)
DEEP SOUTH: Louisiana non-Cajun, Mississippi, Alabama, and Georgia
CAJUN: rural / French influenced Louisiana
NEW ENGLAND: New York (like California, VAST differences based on neighborhood), New Jersey, etc.