This doesn't allow for the specifics of the US, where a woman or girl who doesn't want to have a baby is unable to access a safe, legal, affordable or free termination.
Here, it's relatively simple to end an unwanted pregnancy - no need to hope that their ex (abusive, not abusive, a close family member), their rapist, an in-law, mother, grandmother, sibling, aunt, distant cousin or anybody else will be prepared to take and support a child that the mother doesn't want to carry to fullterm. And there are no massive medical bills, benefits and social housing are available, there is an adequate entitlement to maternity leave and in the vast majority of locations, a good supply of registered childcare (and benefits to assist with the cost) of returning to work.
In the US, that is not the case and therefore there will be women who did not want to be pregnant having no choice but to continue that pregnancy - and to then potentially have people that do not want to take on that child in kinship care, possible homelessness, a huge bill for medical treatment, next to no maternity leave and due to the geographic size, significantly fewer options for childcare that don't also involve the cost of maintaining a vehicle, making it less likely that somebody could be able to work.
In short, whilst here, the vast majority of babies and children that are adopted have been removed purely for their own safety, in the US, babies in particular are adopted because the mother never wanted a baby in the first place but was denied a choice prior to birth - but can make a decision about what will happen afterwards that they feel is in the best interests of the child and potentially protect them from some of the most punitive consequences of becoming pregnant in the country - the financial ones.