In 2019 - before COVID - the fertility rate for all USA women actually dropped below the replacement rate for the first time since the Great Depression.
The only reason the USA population grew in 2019 (and probably 2020) was because of immigration.
Native born USA women have been below replacement rate for many years.
In 2019 - which had a very strong economy - foreign born USA women were below the replacement rate for the first time since records have been kept.
Some people say its was caused by women's lib groups pushing women into the work place. Other's point to economic policies that have forced most families to require two incomes. In the past children assisted on family farms or helped parents in old age. Something, that has seemed to decline with Social Security and Medicare. Might explain the expansion of assisted living facilities. In the cities or on farms, the more children, the better the families overall economic conditions once the children reached working age. But, even in the Sixties and Seventies, as family farms declined, two children households were common, three and four children were not uncommon. It was not racial either. Black and Hispanic friends my age have two or more siblings also. Is it a sense of entitlement or selfishness with a generation that does not want responsibility?
Being military, I have a very mixed group of friends. The majority of whom are military. Most have two or more children. I find it odd because even the younger families have multiple children. The military no longer pays additional money for each child, that ended decades ago. You have some who prefer no children now, but plan to have children later. But the vast majority have at least one child and plan to have another. It may be a case of stability, I do not know. Maybe if the feds/States changed policy and cut federal income taxes by 50% for any family with four or more children living in the household. When I was young, a family I grew up with had nine children. The father used to joke about not paying State and Federal taxes after the ninth child. Maybe that is the way forward?