Actually, the reason the Nazis did not adopt the "one-drop" rule was because Hitler himself had Jewish ancestry. They carefully drew the line just past that ancestor. They used the meticulous German records to confirm who was a "Jew" - whether they considered themselves Jewish or not, in line with Hitler's insistence that Jews were a "race." With modern technology, it appears that many considered "White" in America had more than the "one drop" allowed. The lesson from all this is how illogical racism is.