How did non-German governments and volunteers assist Germans carrying out the Holocaust?
Germans were not the only people who had anti-Semitic tendencies during this time. The Nazis got help from some other governments and even from individual volunteers.
An example of another government helping with the Holocaust was the Vichy government of France. Of course, this government only existed so long as the Germans let it, but it was proactive in helping with the Holocaust. The Vichy government helped to round up Jews and then to deport them to the camps.
An example of individuals helping with the Holocaust can be seen in Lithuania. There had been pre-war anti-Semitism in Lithuania and it carried over into the German occupation. Lithuanians helped round up Jews there, helping to lead to the death of about 90% of Lithuanian Jews.