My wife (Brazilian citizen, US permanent resident) and I (US citizen) will be traveling to Brazil by plane with our 5-month old daughter (US citizen).
Our daughter may not have a passport by the time we depart for our trip. Would we be able to make it through the borders of each country using just official copies of her birth certificate?
No. Excepting some special circumstances that don't apply here like official military travel, a passport is required by the US. Brazil similarly requires a passport. Any airline will simply deny boarding if you show up with only a birth certificate.
For instance, if you go to Timatic and tell it that a US citizen wants to go to Brazil with only a birth certificate, it will say:
No, The travel documents held are not sufficient for the traveler's journey, or they may need additional documents as follows:
Brazil - Destination Passport
Passport required.
You should also review the US State Department's Level 4: Do Not Travel advisory for Brazil. If you do not trust the US State Department, consider also the UK's advice against ‘all but essential’ international travel.
There are also non-COVID health matters to attend to in Brazil depending on where you are traveling, including yellow fever and malaria risk areas, so if your travel is imminent, you'll need to address that immediately.
If you have urgent international travel plans, you can get an expedited passport for your child. I once needed to get a same day passport because the government lost mine, and there was a Swiss couple ahead of me in line with their adopted newborn. Here's a link to the government webpage; consider calling them as well.
Besides the passport as argued elsewhere, at least until a few years ago Brazil demanded visas from U.S. citizens, as a reciprocity measure.
I don't know if it changed, or if there's some exception to small kids or children of citizens. Do you have a visa?
