But that's a different point to what GP was making. It wasn't that children answer differently to adults, it's that they get it 'right' more often than adults. Which is still more about ignorance allowing them to make the same assumptions as the questioner than thought processes. A child might not even be aware that people in other countries might drive on the other side of the road, and so be sure of their 'correct' answer, but most adults know that without knowing the location of this image, the question can't be answered.

EDIT: And if the question weren't ambiguous, you'd basically be telling people the answer, since as soon as you say "assume it's in the US", you give a massive clue that bilateral asymmetry is relevant.