In Path of Radiance, Japan had four difficulty levels: Easy, Normal, Hard, and Maniac. Maniac was removed for the NA release.
In Radiant Dawn, there were still four difficulties in Japan: Easy, Normal, Hard, and Maniac. However, rather than remove Maniac, they removed Easy. The other difficulties were renamed. So it was:
JP Normal -> NA Easy JP Hard -> NA Normal JP Maniac -> NA Hard
That's why you can't transfer an Easy mode file. NA Radiant Dawn doesn't HAVE an Easy Mode in the first place.
And FYI, you can't transfer at all if the Easy Mode data from PoR is on your memory card. It doesn't matter if you wanted to transfer from Normal or Hard, an Easy Mode playthough cannot exist on the memory card without RD freezing. So, just delete the Easy data or move it to another memory card. Problem solved.