Sad, but true. I think I stated here before that only about 1 in 20 here could name your PM, about 1 in 100 your PM-lite. Most Americans are very insular, which is easy to do in a place that's 3,000 miles across. Still, no excuse.
I know a very well off, college-educated woman in the Midwest who once told me that visiting Europe was like having kids, something you had to do, not something you actually relished doing.
I would say only about 5-10% of Americans have any slight idea what's going on in the world. Very few even have an idea what is going on in their state or in the US as a whole.
But, if you are honest with yourselves, you will have to admit that the percentage of very informed "international" people in Britain is probably not that much higher.