So, what's "linked" to Transportation? Cars, Railways, Airports, Harbors... no. Something thus related to roads? A ressource used for roads and its natural environment? But it's not "geography". Car radios?
Another trail of thought, we are looking for something which the USA is compared to the rest of the Western world, very good or bad in. So, normally, Industrialized countries don't have it. Plus, it's more common on the northern hemisphere. So, is it some natural gaz like Ozone? But I'd guess that would be prevalent also in Europe...