No, the accent isn't real, but it's more believeable than most (remember Kevin Costner in Robin Hood? LOL!!)
James, as many of you know, was born in Greenville California. Then when he was real little, his family moved to Modesto, CA - where he grew up (and went to High School, etc.).
Any voice he wants to use - English or American - is just fine with me. He's precious!