In the show Band of Brothers when US soldiers are dropped over France, one of the enemy soldiers is an American born young man with perfect American English. He says he moved to Germany because the fatherland called his family and they went.
How common was this? And what happened to the prisoners of war who were American but fought for the nazis? Were they charged with treason?
Unfortunately, there is not very much specific information about this topic.
However, I found an excellent answer written by u/coinsinmyrocket that may have information that pertains to your question.