OK, there's threads on taking vehicles to Germany and the UK, so unless you're going somewhere else I strongly suggest you find and read them. If you're going to either of the aforementioned countries, than you had better learn quickly how to or your experiences on this forum will get painful really quick.
But, since I'm in a generous mood this evening, you are "aloud" to ship a second POV to Europe on your own dime. I did so when we went to Belgium in 2002. It's not cheap, and you have to take into consideration that every major US base in Europe has a "lemon lot" where you're usually able to pick up a good deal on a second vehicle, many times a local specs one. So unless your second car is something you really can't live without, it might be cheaper to sell it and buy a second one over there.
Last recommendation, go look up the word "allowed" in a dictionary...