It's a stupid idea to learn flying in US but want to work in Europe.
You need to covert your FAA ATPL to JAA ATPL, retake most exams and flight training. It's a waste of money and time
FAA to JAA pilot license conversion « P3air.com
Hold a valid JAR-FCL Class 1 medical
Obtain a Radio Telephony Operator License
Undertake JAA ATPL groundschool training at an approved Flight Training Organization (FTO)
Pass all 14 JAA ATPL theoretical knowledge examinations
Undergo and pass Type-Rating/MCC course in approved TRTO (Type Rating Training Organization)
Pass the ATPL skill test – must be with or observed by a CAA Flight Operations Inspector