I'm a Canadian citizen with a Canadian passport. I booked a flight with American Airlines to Mexico City From Toronto Pearson and it says that "Passenger details are needed to check in".

Flight 1: YYZ -> DFW -> MEX   
Flight 2: MEX -> DFW -> YYZ   

They already took my name, gender and such. It is now asking for my passport number and expiry date. That all seems reasonable. However, when I enter that I am a Canadian resident it asks for:

1) Street or hotel in US  
2) City in US  
3) State in US  

My trip to DFW is only for a connecting flight. The fields are required so I can't submit my passport information without filling this in.  

Is there something I'm missing?