Since it's multiple choice, with four options for each question, a person with no relevant knowledge at all should be able to get 2 or 3 right by random answering. Hence I conclude you have negative knowledge of American English, MK!
I thought I might do a bit better in the British one, since I think I'm more exposed to British than American via reading and TV. But I got 7 in the British quiz and 10 in the American. I had some luck on the American quiz, as there were a few I wasn't sure about.