I don’t think she’s faking it, but I think she’s a bit of an outlier in that it’s a bit more extreme a change than what I’d expect. I know plenty of Americans who have lived many years in England (and vice versa), and their accents became slightly more like their adopted country’s, but the extent of Madonna’s change is atypical. On the other hand, I have one acquaintance who, when I first met him, had a Blues Brothers like Chicago accent. I met him two or three years later, after he had moved to New Orleans, and I swear I couldn’t tell you that he hadn’t lived all his life down there. I’ve never heard such a complete accent transformation in such a short time. I kind of have a theory that musicians tend to pick up/adopt local accents more quickly, but it’s just a speculation based on limited anecdotal data.
New Jersey Singular. It could be plural if you say “Youse guize”. Short NJ Plural seems to be “youses”.
It’s possible; I’ve noted that singers performing in a foreign language–even one they don’t speak at all–often show little sign of their native accent while singing.
I have a musical background, but I’m not an active musician, and I tend to absorb accents extremely quickly. I’ve been known to pick up significant elements of an accent in the course of a single conversation, without realizing it. (On one occasion, I learned that the guys on the other end of the conference call actually thought I was an ex-pat who was slipping back into their accent as we talked.) I always return to my native hodgepodge accent eventually–though I’ve been known to get “stuck” in an accent I put on for a role for up to a few hours at a time.
There’s a story Isaac Asimov told where he was watching an interview of Peter Ustinov on TV. Ustinov demonstrated that he was capable of speaking in a perfect American accent. Asimov turned to his wife and said, “If he can talk normally, why does he bother with the British accent?”
Of course, he was joking.
I assumed the OP was a joke or making fun of another poster. But if not, Crotalus has it right.
I remember this kid in GA telling us “Y’all shur dew taawk funny.”
How’s about you stick to 1) not using big words like ‘assentation’; 2) not writing OPs making big assertions about language when you don’t know the first thing about it. Please. You’d do us all a favor.
Also, it’s ‘half-baked conspiracy theories’ - the theories that are not fully baked.
Nonsense. I have been called y’all when there was no one there but the speaker and me in Oklahoma, Arkansas, Texas, Tennessee, and Georgia. I have known many people from those areas who used “y’all” in place of “you”, and not a single one of them used “you” for singular. Not one. In fact, a significant minority say “all y’all” when talking to a group.
For the record, I have also known many people from those areas who never used the word “y’all” .
“Y’all” is a contraction of “you all”, first off. Second, using it as the singular is incorrect according to the usual usage.
Second, the difference between “y’all” and “all y’all” is the same as saying “You need to do this” to a group versus “All of you need to do this”. One is a more general, non-specific way of saying something needs to be done by some members of the group, and the other is saying that each and every member of the group needs to do something.
For example, if I was to go to a group of people and say “Y’all need to make sure the recycling bins get taken out”, I’d be saying that the group needs to ensure that the recyling bins get taken out. However, if I said “All y’all need to take out your recyling bins” then I’m saying that every member of the group needs to take out their individual recycling bin.
Funny thing is, no one really talks like that. The New Jersey accent people think is real is only from a very small area in an already small state. It’s the area right next to New York and is really a spill over of the New York accent. I’ve been asked many times why I don’t have a New Jersey accent. I do. Just remember, James Gandolfini came from Bergen County where a lot of the Sopranos was set and filmed. He needed a voice coach to get Tony Soprano’s accent.
Oh shit, not this again.
Ah, the “everybody has an accent except for me and my kin” argument. 
FTR, I find some accents/affectations really, really grating (I want to strangle Paula Deen with a violin wire every time I hear her, also, where the hell did she come from?), some sound cute. It’s a matter of taste.
My understanding is that, outside of the US, the English pronunciation that’s generally taught is UK English, most likely RP/BBC English. You’ll pick this up now and then when a non-native speaker is speaking well enough to mostly drop their native accent, and sometimes even before that. (ISTR hearing it from some Russia Today presenters, for example.)
Actually, this is a variation on that: The “everybody has a horrible speech impediment except for me and my kin” argument.
My family lived in England from '83-85, when I was between the ages of 12 and 14, and I picked up a British accent almost immediately. Imagine my disappointment upon realizing that, among Brits, a Yorkshire accent was nothing to brag about. 
(Americans loved it, though: in college I spent a summer going door-to-door for an environmental group, and when I’d get bored I’d dust off the ol’ accent. It didn’t help with donations, but it amused me…and it took a little longer for people to close their door in my face. :D)
I can’t imagine that he needed much coaching: Bergen County is just across the bridge from NYC. I have a lot of family there, and every single one of 'em sounds like a character from The Sopranos.
I’m from Kansas City, and have this accent. Though (probably due to my age) I mostly associated with Johnny Carson, Walt Disney and folks like that rather than newscasters. Walter Cronkite is from Kansas City as well, but by the time he was nationally famous, it had mutated somewhat.
It seems to be the ISO standard American accent.
His real accent is in just about every other movie he did.
Until he was 10, then his family moved to Houston, and he stayed in Texas up through his jr. year of college, at which point he became a professional radio broadcaster (1935).