a. You will be branded as an American by your clothes, by your speech patterns, by the way you move and interact with others, by your lack of fluency in the German language, by your early dinner hours, and by many other factors.
b. You are a target for being pickpocketed by virtue of your being someone who potentially has more wealth than the person attempting to steal from you. Take appropriate precautions.
c. The Apple Watch, the iPhone, any iPads or iPods are well known in Europe. In 2017, smartphone sales in Western Europe amounted to more than $56 Billion. They are ubiquitous.
d. Apple allows back up of all its products through the Cloud. Back up everything. Install the "find my iPhone" app on all your devices. In the event one goes missing, try to find it and if that isn't possible, wipe it of all data.
e. The latest Apple phone 4 with bells and whistles costs a little over $500. That's not a king's ransom, and you would probably be able to absorb the loss if you don't have Apple Care, which is what I think they call their program that covers you against loss and breakage.
f. Call your homeowner's insurance carrier and get a rider for your watch. I got one for my Rolex and it costs less than $100 per year to protect against loss or theft.
Relax. It's a vacation. The roving bands of gypsies and street criminals are not likely to find you.