Yes, most of those who liberated Hitler's camps were Christians of one denomination or another. But Jews were represented in the American armed forces during WWII in a percentage greater than their percentage in the American population. There were over a half million Jewish American servicemen during WWII and some were involved, obviously, in the direct liberation of the camps.
You are distorting history when you say that American Jews "mostly sat tight in Manhattan" during this trying period.
I agree. All my Jewish Uncles but one served in WWII, and my Jewish father would have, but he flunked the physical three times because of a duadenal (sp!) ulcer. He wanted to serve.
Jews fought (my late father) and died in WWII.