Start by naming any country that France borders. Then name any country that borders any of those countries. Then keep going until there are no more countries left to name.
I definitely would not call Mt. Rushmore a natural wonder. Yes, I know that the mountain itself is a natural geological feature, but it is only famous because of the presidential sculptures which are definitely not natural. I would suggest replacing it with a purely natural wonder from the same state, such as Jewel Cave or Wind Cave.