>“to restrict citizenship by birth within the United States to the children of parents who are of a race which is eligible for citizenship”—i.e., whites
White was also not considered a race in the 20's. There were Nordics, Jews, Irish, Eastern Europeans, and Southern Europeans. American eugenicists also were very much into "building" a race. They would have family breed competitions at fairs where families would compete like dogs or livestock for who were the best breeding stock. It wasnt a white vs colored, it was a tall, intelligent, hard-working, disease-free, group of mostly northern europeans vs anyone short, stalky, diseased, epileptic, mentally deficient, criminal, promiscuous, obsessed with art, etc. For instance, Irish were considered a problem because they didnt work hard, were obsessed with art and music, were short, and susceptible to tuberculosis. Mind you, this is not scientific fact, this is just the nonsense they spouted at the time. They also believed in a thing called "Germplasm" which roughly translated to gene pool, but of course even today we're not exactly clear on what's genetically inheritable and what isnt.
I should also mention, this is the deeply disturbing origin of the progressive movement in america. Using what they thought was superior scientific understanding of the natural world, the IQ test, birth control, the gifted student program, the use of performance metrics in school and workplaces to justify glass ceilings, firings, mass deportation, and mass sterilizations of anyone deemed deficient in any way by society. The work americans did to create a legal framework for eugenics would be borrowed by the Nazis to create their own legal framework for the deportation and final solution of the jews.