Noggin as you quite rightly point out the FAA has no requirment for FM immunity this is probably because the americans are smart enough and have enough space to not let commercial radio stations use the frequencys hard up to bottom of the navigation band.
So an FAA registered aircraft will be just as subject to disruption of navigation imformation as a european aircraft and so to fly IFR in europe FAA registered aircraft have to meet the FM immunity requirment.
In my view the aviation community should have objected more strongly at the first hint of this requirment to do this we must activly support AOPA and the PFA with letters to MP,s MEP,s and the press.
This has cost us all a great deal of money and should be a warning to us all that if we dont stand up for light aviation we will lose it........now rochester airfield is being eyed up by the local planing authority as a site for "development" now just how few of us are going to send a letter of objection to the planing authority.