If a woman is going to deliver a baby in the United States, and the doctor on call is male, is it ok for him to deliver the baby, if a female doctor is not on call?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

It is not permissible for a woman to allow a male doctor to treat her, or to be her obstetrician or to look at her Awrah (parts of body that must be covered) except if there is no suitable woman to perform that.
In a word, it is permissible for a woman at the time of compulsion and not having any alternate to consult a male doctor at the time of delivery or for any other treatment.
Allah knows best.