Refer to the document entitled '
Issue a Title 14 CFR Part 61 U.S. Pilot Certificate on the Basis of a Foreign-Pilot License' under the FAA
Flight Standards Information Management System
There is an abbreviated 40-question test for the inclusion of a restricted US instrument rating on a restricted (61.75) private certificate. It's called the
Instrument—Foreign Pilot knowledge test and you may be able to take it a handful of centres in Europe. Additionally it will be necessary to repeat the foreign licence
verification process with the FAA Airmen Certification Branch in Oklahoma. You'll also need to pay a visit to a FSDO to have the 61.75 reissued with the IR privileges.
For the medical, read 14 CFR 61.75(b)(4). The issuing State must be identical for the JAA licence and JAA medical.