What was the American public’s reaction to the Holocaust in the immediate aftermath of WW2? Was it recognized as uniquely horrible, like today, or was it seen as just one more awful story following years of the same?

This is /u/Kugelfang52's special area of expertise:

Did American soldiers who saw the racist atrocities of the Holocaust...have a moral awakening or did they go back to eating nonchalantly at whites only diners?
What does it mean for the Holocaust to have been "rediscovered in the '70s"?
Why was it official US policy not to use the word "Jew" in connection with the Nazi concentration camps?

Also have a look at what /u/kieslowskifan wrote about why the death camps were not mentioned much during the TMWC at Nuremberg featuring a mention of American Supreme Court Justice Robert H. Jackson.

While this is more about German memory politics/historiography than that of the USA, you can listen to Episode 57 of the Askhistorians Podcast or read the transcript I prepared from an interview of /u/commiespaceinvader, which details the argument about whether the Holocaust was uniquely horrible in history or just another awful story like many others.