txp is dual national USA/CAN. Airline has no issues with either passport for flight to CAN or USA.

APIS details and actual passport used at inspection does not have to be same. Folks asking about which passport to check-in on this thread are getting hung up they have to be match. Authorities are not going to deny entry because of differences between APIS document and actual document. APIS provides details on who is coming in but any "persons of interest" will be matched primarily on name/DOB and not travel document#.

Thus my advice is to OLCI with the passport that allows for it (eg no visa required). And optionally present all passports to airline.