Current law accepts abortion on demand. It is wrong about that too.
To be honest, though, descent through the mother is actually easier to prove. Questions about the real mother are a lot easier to answer than questions about the real father.
Under American law, the Husband of the Marriage is the legal father. Being that he is generally the person who raised the child, to what country he holds allegiance, likewise influences the child.
I am adopted. I have no idea what my Biological father thought. I followed what my Adopted father thought.
Doesn’t matter.
By Birth Citizenship is either jus soli or jus sanguinis