One prob with a bike from US is the lights will have to be adjusted. Not just the headlight, which will need replacing with one with a Europe stamp on it, but the wiring to the indicators will need changing. I think I am right in saying that in the US they are on permanently then flash for turning. This is not acceptable in Spain as they have to be off unless actually being used to indicate a turn.
Some people have probs bringing bikes into Spain. I brougt a Suzuki VL800 from UK. Only difficulty was actually getting a headlight for driving onthe right. You can't just redirect a UK one due to the shape of the beam.
Good luckand ride safe.