I was a bit confused by this concept as well...I understand the fact that each individual action potential is the same, but I feel like input and output, which are patterns of many action potentials, are a different story.  Eyes and ears receive input in very different ways (sensing light v. vibrations), and so the patterns of input signals that are sent through the nervous system when we "see" lightening are not the same as the patterns that come from "hearing" thunder.  And if one were to somehow "switch" the cables, so as to send visual signals to the auditory box, and auditory signals to the visual box, then I think that the perceived output would be quite different from the kinds of sights and sounds that we are used to...wouldn't they?  Maybe these types of phenomena are similar to what happens to individuals with synesthesia?...although I don't really know enough about that condition to make a connection.  Anyway, just some things to think about.