The FDR thing is fairly well known. The recent Ken Burns doc on US policy and the Holocaust is worth watching on this. But during the war FDR faced a choice of putting resources to ending the war or hoping that bombing would have some impact on the holocaust. But there wasn't really any evidence that bombing camps would make a difference. There were thousands of camps and they could just moved populations around and repurpose other camps, or they could go back to the strategies of earlier in the war and just machine gun them down. FDR realized the only realistic option was to defeat the Nazis.