From working in a call center (and hubby was still taking calls from all over the country just a few months ago, so he verifies) I can tell you that there are still heavy regional accents.
Heavy regional attitudes, too...ooh those people from up near where my mom came from (upstate NY) just START with attitude, and when you're talking to a laid-back northwesterner (transplant from CA, the CA still comes through sometimes) that is just NOT the way to start things off! Though I found that if I put on a North Dakota/Wisconsin sort of accent it could calm things down a bit so they'd hear that I was working to helping them, despite the attitude and threats.
Jinkies I do not miss those calls...Especially the lady that put her 4 year old on the phone for me to explain why his birthday present wasn't going to be there on his b'day, when SHE was the one that ordered the enormous toy only 2 days before, it was lucky it got on a UPS truck since it was supposed to go by white glove shipper, and, oh, there was an ICE STORM outside that halted UPS delivery that day near Schenectady! I had co-workers popping up like prairie dogs when they heard my voice change once I realized that she had put her small child on the phone...
All that to say, regional accents are still very much alive, however, I have noticed the California accent (ya know, like, and just the way of drawing out certain words) spreading. I once went to an all ages club in Spartanburg SC, and I heard college students from the area, speaking with a Southern accent, with a big of deadhead/rasta influence, with a CA veneer spread over the top. I can imitate accents well, but THAT one, along with New Zealand and South African, I cannot do for the life of me.