I'm American and I get mixed results between 89% American and 53% British on my normal accent. My pronunciation of "call" and "to" seems to tip the scales towards British and most of my other words are not strongly highlighted.

I can reliably fake a British accent although I seem to get stuck on frog and store still sounding American. When I do the stereotypical Texas style "yee haw" accent I get 99% American.