Darth Vader was voiced by James Earl Jones in the original trilogy. Jone' s voice is very distinctive as being deep and booming, but although he was born in Mississippi, his accent in his roles typically is General American, free of regional characteristics. read more
In the original trilogy the Empire represents somehow the British Empire and the Rebel Alliance the revolutionary Americans (there are also other lectures, like the Roman Republic and Empire, etc.). So high rank officials are set to have a British-like accent whereas the rebellious people from the faraway colonies will have a more American one. read more