See if you can find a book called "Am I a Murderer?: Testament of a Jewish Ghetto Policeman" by Calel Perechondnik. It's a fascinating autobiography on one Jew's attempts to survive a slaughter.
I think that millions of "good Americans" would just shut up and keep their job on the "Munich-Aushwitz Rail Road", and most cops would go on house to house confiscation raids.