The current queen rules not only Britain but Canada, Australia, New Zealand, and a few other places too, but I don't think anyone would claim that makes her one of the most powerful people in the world! Although I do remember, some years ago, meeting an American student in Britain who believed that the Queen really rules Britain. She hadn't heard of Tony Blair and said "What's that?" when I said he was the prime minister. She seemed to think Elizabeth II reigned in much the same way as Louis XIV.