I think you would be very surprised. As a non-US citizen i know almost as much about US politics as my own country's. People around the world have an interest in US politics, it is nothing like asking someone about Japanese or German politics. My guess is that many countries have a proportion of informed people that is not massively far off the US.
If you watch Newsnight or read a broadsheet or similar then you'll probably be well informed; if not then your preference is probably based on your music taste or the media coverage of Romney's underwear style.
To be very surprised then the levels of knowledge would suggest we might get a properly informed vote here sometime.
