American eugenics was a model the Nazis studied. Rockefeller money helped fund German racial-hygiene science, Germany's 1933 sterilization law borrowed from Harry Laughlin's template, Heidelberg gave him an honorary degree in 1936, and Buck v. Bell was cited by defense lawyers at Nuremberg. The influence is documented, but the episode is explicit that America did not cause the Holocaust.
Hitler's reported praise of Madison Grant's book rests on secondary reporting. Scholars debate how decisive American models were compared with German racial thought, how culpable the Rockefeller Foundation was, and how much the Nuremberg citations mattered.