It's fair and accurate to say that the US military and government knew more about the "final solution" than they told the public during the war. Critics claim that the Allies could have and should have bombed the camps, the rail lines leading to them, and so on.
Roosevelt, Churchill, Marshall, and that crowd reached the strategic decision that the best way to end the genocide was to crush the Reich and win the war quickly and decisively. It's hard to fault that conclusion. Bombing Auschwittz would have slowed the slaughter, but not stopped it; sending the Nazis to the dustbin of history and Hitler to hell was the only way to bring the Shoah to an end. That was the plan they chose, and that's what they did.
This mythology has been extremely successful and influential; nevertheless it is entirely wrong.
I agree that it's entirely wrong. I disagree that it's been extremely successful and influential. I believe that the prevailing view is that the US and the Allies did a great deal of good, but could have done better and should have done it sooner, That does not diminish the good; it's something we should note and learn from.
True, but remember that the American Jewish community was in many ways against widespread publication of information on the Holocaust, because they thought it would engender a backlash. The last thing American Jews wanted was to create the perception that the war was a "Jewish" war.
Moreover, the public was deeply suspicious of attrocities claims, following (false) reports of Germans bayonetting Belgian babies in the First World War. If you want to fault the US Government for not making what they knew of the Holocaust more widely known, you can do so, but I think they felt they had good reasons for not doing so.
On everything else, of course, I think we agree.