Originally Posted by
Dovster
When I fly to the States:
1. I show my Israeli passport for the Security check in TLV.
2. I show my both my American and Israeli passports for check in at TLV. (They need to see the Israeli passport because it has the Security sticker on it and the American passport to know that I will be allowed into the States.)
3. I show my Israeli passport to Passport Control in Israel.
4. I show my American passport to Immigration upon arrival in the US.
5. I show my American passport at any airports where I am going through a TSA checkpost.
6. I show my Israeli passport upon checking in for my return flight to Israel.
7. I show my Israeli passport to Passport Control in Israel.
The OP will only go through TSA once, and that's on the return from Brasil. After clearing Immigration and Customs in ATL, he'll have to go through TSA to get to the flight to YYZ. He doesn't need a passport, I would hope that TSA can figure out a Canadian driver's license. If not, either passport will do, as it's not important beyond matching a boarding pass to some form of photo ID for TSA purposes.