What could the United States and other countries have done before the war to stop the Holocaust?

Answer

To stop the Holocaust the United states and other countries could have passed laws that made anti-Semitic illegal.

Explanation

Holocaust was genocide which was carried against Jews and other groups. Millions of people including homosexuals, Jehovah witnesses, soviet prisoners of war and political dissidents also suffered mostly oppression and death under Nazi tyranny.

Antisemitism was the discrimination against the Jews. To prevent this before the war the nations could have passed the anti-Semitic law and make it illegal so as to protect the Jews and other ethnic groups from being hated and discriminated

This is a complex topic, because there was lots of anti-Semitism in the United States and elsewhere during this time, but many think the Allies could have bombed the train lines to the concentration camps.