To a Canadian, a New Zealand accent can easily be mistaken for a British one (I know; my mom's from New Zealand and she's often been asked where in Britain is she from).
Anna
Okay then, I'll just say that more New Zealanders seem to either a) be able to convincingly fake an approximation of American or b) choose to learn to fake American. Because Nicola Bryant and other 'Amercians' on BBC are generally so far off base Americans go into shock when hearing them.