They don't have the United States or Independencia in their world, so her accent is interesting to Rory. He collects them for later use in his work. Which totally doesn't involve pretending to be other people. But he gets the connection.

"Where's that?" Ceilidh finally asks, curiosity getting the better of her sulking.

Rory was going to ask the same thing, but sometimes it's nice to have a small child ask the question. People will explain things more openly to children than adults.