Green card for the baby born outside USA

Can I ask from which country u come to USA and which documents they see at port of entry
We entered the US from the Bahamas, Nassau. It is a pre-clearance port with US CBP officers. All we need are birth certificate and travel document for the child, SusieQQQ is correct. The only issue is that the officers there do not understand the regulations and told us that the child needs a visa. We went to the US Consular at Bahamas and was offered no help. We ended up reaching out to the US Customs at Washington D.C. to resolve the issue.