It seems that some British actors oftentimes speak a more authentic American accent than even American actors can. Some notable actors in this category are wide-ranging, if always reverting to their native British tongues in interviews or when interacting with fans.
Robert Pattinson is one who seems to be a lone standout in acquiring an American accent and using it in real life. As strange as this might sound, it was apparently a psychological mechanism, according to him.
In past interviews, Pattinson addressed his ability to do a convincing American accent and how it helped separate himself from his own self. To cope with fame, it proves Pattinson as an offbeat acting case study.