1st thing you want to make sure You have a drivers licence that will enable you to drive Anything bigger than a Car or Suv. Also Emission standards and specs on motor vehicles in the US are different than in Europe. As stated above, Europe is So So beautiful, in some instances 2nd to none, but it did not become that way over night, So yes you will find places where it is impossible for cars to go, let alone a camper or a bigger class c.
Look: you wanna hop around Europe? there are so many cheaper solutions. Europe has a Great transportation system, you can take an Air bus from London to Frankfurt for $30 for example. You can get a Euro Rail pass and see Europe on the train, OMG it's so beautiful. Also Take Advantage of Rentals if necessary. If you stay in one place for an extended stay, don't worry, everything is so close that you most likely won't need a car. hope this helps