Let’s play it a few ways since it’s a hypothetical.
1) All the guys admit to not wearing a condom and to having sex with her and they all admit that they could be the one.
2) None of the guys will admit to being the father.
And then there’s an angle on the hypothetical (with a change in initial conditions):
3) The woman was the victim of a rape by a foreigner but nothing else changes (birth by US citizen woman on American soil).
4) The woman truly doesn’t know who the father is (because she was blind drunk) but other people swear it’s a foreigner because they saw them together. (you can also tweak this one by having the foreign male claiming paternity even though the woman denies it)
I bring this up in a way because the whole issue of ‘legitimacy’ used to be applied to any child born out of wedlock but our ideas about these things have clearly changed over the last few decades. But it’s still a useful exercise to examine it.
The baby born on us soil to an
American Citizen is a US citizen.
If unwed at time of birth to decide if a child had two USC parents I would guess one would apply standards for passing citizenship by father to a child born outside (and outside of wedlock) of the US. The father must be a citizen. There must be clear and convincing proof of a blood relationship with the child. He must acknowledge the child under oath (or have a competent court declare such)and agree to provide financial support until the child is 18 years old.(unless the father is dead) The child must also be legitimized under laws of residence of the father before the child is 18.
see 8 USC 1409