Actually, as I wrote it I realized that I didn't know myself with any accuracy. I know Trafalgar is in Spain, and I guessed that it was down near Gibraltar. I am glad that I was not too far off. I would have been embarrassed had it been in the Bay of Biscay or anything.
As for the other quarter of the world, you may be right. If someone asks where a battle of the US civil war was, I'm not going to be far wrong if I stick a pin in somewhere between Virginia and the Carolinas for the most part, but that's really why I specified a British person. Even then, I would guess that most Americans couldn't place Iwo Jima with any accuracy, but then most British people probably couldn't place Ypres very well. In short, people are crap at geography.
Did everyone do
this quiz? Or even
this one?
ETA: I got 89% for the latter of those, which makes me suspect that some are cheating. I think my furthest was 27 miles for Timbuktu.