The medical issue is quite simple, the FAA isn't interested.
Your 61.75 issued licence is only good if your licence against which it is issued is valid -you have to have a class2 medical that goes with your licence - when it expires so does your EU licence and hence your 61.75 PPL licence is invalid.
You also need a current flight review for your EU licence and the a current FAA flight review.
For the record if the bill before congress that will allow flying on the basis of a driving licence in lieu of the present FAA clas three (airplanes under 6000lbs, less than seven seats) one would need to surrender the 61.75 if one wanted to fly medical free under an FAA PPL