I think the most important part of this discussion is being left out. Do you have a pot of gold to work with or are you on a shoe string budget?
If money isn't a problem and you don't want to worry about a hassle, either buy something there that fits your needs or find a reputable RV rental company in Europe and rent from them. That way you get something that you know will work in that country.
American vehicles are HUGE compared to European vehicles. The last thing you would want to do is bring in a Huge American Truck and Camper and stick out like a sore thumb and have trouble navigating the narrow streets over there. Bringing your own vehicle I don't see as any sort of practical solution to this problem.