What could the United States or allies have done to stop or at least bring attention to camps and murders occurring?

United States or the allies could have stopped the policies of appeasement for Germany before the war erupted.

Explanation:

The Us and the other European countries who had been on the winning side after the world war 1 were in a increasingly terrible policy of appeasement of the German ambitions which was suffered until 1938 during which the persecution and sometimes murder of Jews had started as the collective world turned a blind eye to the slaughter.

This was because US was afraid that their own previous dealings with he country had not been kind and speaking out on this would have caused more issues whit the Nazi German Government.