Only a few non-US airlines are authorized to issue TSA PreCheck boarding passes even if they have your Trusted Traveler number on file (if transferred from a US airline's res system). If the first US flight segment is booked with the AA flight number you should be able to do an OLCI within the normal 24-hour period and get a new AA boarding pass (either print or mobile) with the PreCheck symbol. Pretty sure I've done it under circumstances similar to OP...though it can also be issued after clearing customs and going to the baggage recheck counter. (IIRC Air Canada and WestJet are the only non-US carriers able to issue PreCheck boarding passes for eligible Nexus/Global Entry passengers who add their Trusted Traveler number to the booking.)