USCIS doesn't issue visas, so when the Consulate says no, State sends the case back to USCIS with a recommendation they revoke their approval. Then USCIS sends a Notice of Intent to Revoke to the petitioner, giving an opportunity to provide a response. Sometimes they still revoke, (usually) but sometimes they send it back to the Consulate for another interview. That's no guarantee of a visa either. No debate on any of that, however this is a specific question about a petitioner's birth certificate. I've never heard of a Consulate denial based on determining the petitioner was not a US Citizen. I'm saying US Citizenship is not the reason a Consular Officer might want to review a petitioner's birth certificate. There are other reasons, most commonly when its about something else, when the petitioner was NOT born in the USA. Example. Is the petitioner married to their brother or sister? LOL