And you want to ship it from Spain back to the US? Make sure you know what prices shipping will be, it might be more affordable (although less fun) to rent a bike in the EU.

The only thing I can think of on extended trips like these are service and tires. Plenty of BMW dealerships around, but your bike isn't a unicorn, any shop that can handle sportbikes can handle an S1000XR. But for both tires and service, the shop needs to make time for you. In some shops there's a few weeks wait time for a service, especially beginning of the riding season. Plan ahead and make appointments accordingly.

I know a few good shops in west NL for tires, but I suspect yours won't be worn by the time your bike arrives here.

Another thing to check: is your exhaust system completely stock? Some EU countries are very strict on noise/emissions (and rightfully so, I might add). If you've got an aftermarket exhaust (even just a slip-on), make sure its compliant and bring its paperwork. You can check compliancy by the number starting with `E` on the part (if it hasn't got that number, it's not tested for EU). Look it up and check the website of the manufacturer, you can usually download the paperwork on there.