An FAA CPL/IR is of very little use in europe. It can't be used without a validation for commercial purposes on EASA aircraft. You will get only one validation, the idea being that you have that time to convert your licence to EASA. The IR is worth getting in that it is relatively easy now to use the competency based route to convert it to an EASA IR, and of course you can fly on it privately. A skill test, air law written and human performance written will allow conversion to an EASA private licence.