The birth rate amongst Americans (Whites) is low because of the degenerate culture promoted by the Zionist owned media which discourages family values/traditions and promotes extreme feminism, homosexuality, lesbianism, and sexually depraved behavior.
Women are discouraged from having and raising children. The portrayal of giving birth to and rearing children as something "oppressive" and "restricting" has instilled a mindset within the average American (White) female that having Children = bad, while on the other hand a life of having multiple jobs, indulging in obscene and promiscuous sexual acts involving multiple partners, getting drunk at clubs and parties, etc is depicted as something to "desire" and strive for.
Which has lead to many social problems, including high abortion rate amongst White Americans, drug/substance abuse, besides a low birth rate.