I don't think this varies from state to state since passports are nationwide, but for us, we had to wait for the new bc to get a passport. There wasn't any paperwork we had that would get us a passport without the bc. Maybe if the child was born in another country it's a different set of circumstances because they come home with a visa, but for a child born in the US to US parents, you need a bc.You are correct. My son was born in China where adoptions are finalized in country. We have a Chinese birth certificate with our names listed as his parents which is why technically we do not need to get a state birth certificate. It's really only for convenience.
We were able to get a US passport b/c of all of the pre-paperwork we filed with the State Dept and USCIS (DHS) prior to going to China.
Very different from a domestic adoption.