FWA
For whatever reason, we have more RT problems with American aircrew than those from many countries where English is not their first language. It makes me wonder if European aircrew have similar problems on your side of the Atlantic. It's as if European ATC speak and American ATC speak are different languages. I also have a theory that long haul US aircrew get across to Europe less often than long haul European aircrew fly in the opposite direction. As a result, the US aircrew are less used to hearing European style ATC.
Still, we always get the message across in the end. Well, almost always. Occasionally, after the fifth time of offering someone a MIMKU direct to LEGNI routing, you give up and send them direct to Newcastle instead...