There is nothing new in this. A man who is the legal father of children has always been obliged to pay child support. This is the way it has always been in America.
That is not true. Forced child support really didn't start until the mid 20th century when the American people suddenly decided they should let the government into their houses.
Well, it has always been the case in America as long as I have been aware. As long as the couple is married or the man's signature is on the birth certificate, the man was considered the legal father. I think that because of such a high divorce rate these days and because of the problems of collecting child support, the law has been confirmed in the various states more recently. It is called The Presumed Father Law:
Presumed Father Laws | LegalMatch Law Library
This link outlines the law.
This quote is from another page and focuses on the type of situation in the OP (this quote is not from the link above):
"if a blood test proves that you are not the father, whether the real father is made known by proof or not, then the presumed father must still pay child support. Also, if the biological father is made known to the court he will not be obligated to pay child support but the custody and visitation will be shared only between the biological parents involved.
By law, a presumed father must pay child support.
"Under the Child Support Enforcement Act of 1984, it is against the law for any father, presumed or assumed, to not pay court ordered child support to the custodial guardian, regardless of joint custody. Federal laws permit the interception of tax refunds to enforce child support orders, and other methods of enforcement include wage attachments, seizure of property, suspension of a business license, and in California, driver's license revocation. In the event that none of these attempts are entirely successful, the court of law that issued the child support order can hold the father in contempt and, in the absence of a reasonable explanation for the delinquency, impose a jail term."
Presumed Fathers Act: Should a Man Pay Child Support Even If He is Not the Biological Father? - Yahoo! Voices - voices.yahoo.com