This will help you out
https://help.cbp.gov/s/article/Article-724?language=en_US
If traveling domestically, a passport is not needed but If you are driving into the United States (U.S.) and have not yet received a birth certificate for a U.S. or Canadian citizen infant, the U.S. Customs and Border Protection (CBP) Officer will accept: the birth record issued by the hospital, a letter on hospital letterhead or a letter from the doctor who delivered the child providing details of the birth, including the name of the child, time and place of birth, and the parent(s) name.