Yes. Just rename the .NDS rom and the .sav file with matching names. E.g. if your EU .SAV file is named as PKM Black(E).sav while your US rom is named as PKM Black(U).NDS, so what you need to do is simply change the (E) .SAV file to : PKM Black(U).sav. Make sure that every word...capital letter, spacing, etc. are the same between the .SAV and the .NDS. As simple as that. And don't worry....no side effect. But keep a back up for pre-caution.
