How common were american citizens fighting on the German side in WW2.

by Spitfirearmy1

[Light spoilers] Watching band of brothers there is a scene where an american born German is found with captured German troops, he says his family is all German and answered the call to fight.

Was this a well known occurrence?

What would be the punishment for an american caught fighting for the Germans?

Thanks for your time.

coinsinmyrocket

A similar question was asked last month and I provided an answer to it, here.