Why Use American Children?

I just obtained this movie on tape and was completely puzzled as to why the children were so obviously American.

They all had an incredibly authentic European look about them. Clearly wardrobe and hair were located in Germany. None of them seemed to have any air of Mousketeers or sunny California on them at all.

Roger Mobley (used to love him on Fury) had an incredibly exotic look about him, even with the hat. I tried to envision that the movie was simply dubbed into English, but honestly, they could have given Mosley the Emil role (he stood out more than Bryan Russel anyway) and used English children, if they feared German accented waifs would be too much trouble.