It has been fashionable lately to bemoan Americans', especially young Americans', ignorance of the Holocaust. But there's so much ignorance of history in general that I don't see these statistics as particularly surprising. I daresay that Americans, even millennials, still know more about the Holocaust than they do about many other historical topics, about which they know nothing at all. In fact as a classical musician and as one who loves the authentic Germany of many centuries before 1918, I resent it that most bookstores' "Germany" history shelves tend to be dominated by books about the Nazis, as if 1933-45 were the only twelve years in all of German history that matter.
However little millennials know about Nazi atrocities, I bet they know even less about numerically greater Communist atrocities, which is why the work of the Victims of Communism Memorial Foundation (even if I disagree with its Americanist orientation) is so important. So yes, history education needs to be improved, but in all areas, not just this area. I was lucky in that I had an excellent 9th grade world history teacher, and read a lot on my own, but many were probably not that fortunate, and why do high schools require only one year of non-US history?