I recently started reading Edwin Black's book "The War Against the Weak: Eugenics and America's campaign to create a Master Race" and what he seems to be asserting is that the American eugenics movement of the progressive era is what inspired the Nazis' ideals that eventually lead to the holocaust.
How true is this? I have always been aware of the eugenics movement and it was touched on briefly during my schooling, but I have never seen anyone else draw a correlation between American eugenics and the creation of Nazi ideals. It wouldn't surprise me, but I'd like to know more about this subject from other sources than just his book.
This is a tricky sort of historical question. If the question is, can we trace a genealogy of ideas from the American eugenics movement to Nazi Germany, and from there to the Holocaust? — the answer is yes, we can. It is actually very easy since the Nazis were happy to point to American influences. Madison Grant's The Passing of the Great Race (1916) reads like a primer in how to justify an ethnic cleansing. (Hitler apparently called it "his Bible.") The advocacy and studies of compulsory sterilization movements by people like Harry Laughlin was directly cited by the Nazis in defense of their own (much larger) sterilization program. The connection between Nazi eugenic ideology and the Holocaust is not quite as direct as it is sometimes made out to be, but there is a real connection (it is just a little more roundabout than the simplified version). So in a sense you can see the American influence.
On the other hand, if you are implicitly asking a counterfactual (which is what a "strong" version of this claim would be doing), i.e., if the American eugenics movement hadn't existed, would the Holocaust still have happened? — that is very hard to answer, but I am inclined to say, while the US movement certainly was leveraged as ideological support by the Nazis, the Nazi racial hygiene movement was in many ways independent of the American strain of eugenics, only borrowing from it at very specific times (e.g. to justify sterilization on the basis of US studies that sterilization caused little harm). It is not entirely clear how much of the Nazi ideology was really American in origin, or whether citing ideological heritage to the United States was a propaganda move to say, "even they are doing it." I am just not so sure I would lay that much responsibility at the hands of a few books; the forces that led to the Holocaust were deeper than Madison Grant, deeper than Harry Laughlin.
So I would be more cautious than Black at drawing this direct line of causation. There were interconnections between the programs. There were mutual admirations and citations. But do we really think that Nazism would haven't existed without the US writings? I find this a dubious historical claim.
Black's work is not bad from a research standpoint but he often goes for the most sensationalistic interpretations possible, drawing thick, direct causal arrows where most historians would see murky interactions at best. (His IBM and the Holocaust also suffers from this approach. Were Holerith machines necessary/useful for the Final Solution? Yes. Does that mean IBM has complicity in the Holocaust? Not really.)
The other side of the Holocaust was of course rampant anti-semitism and hatred for certain ethnical groups. That has been present in Europe for centuries, against specifically Jews and gypsies (Roma, Sinti and the third group whose name I always forget).
So while much of the eugenics stuff neatly tied in with what the Nazis wanted, as restricteddata explained, it's impossible to pin the other half, the hatred-half, on eugenics, much less American eugenics. Jews were persecuted in Europe way before the Thirteen Colonies were even a thing, the sentiment was not new.
Like so many things mired in hate, the Holocaust is a terrible coming-together of many ideas and awful 'traditions'.