T3 intl arrival:
clear CBSA immigration, collecct bags, clear customs, take bag upstairs to other end of terminal for US deparrture, check in AA, drop bags off, clear CATSA flight security check, clear US CBP immigration and then you are at the US departure area.

2.5 hours can be tight depending on the time of day you arrive and depart. There is a rush of multiple intl heavies arrival at certain times of the day and there is rush of US departure at certain time of thhe day and day of the week.
We need to know your flight times and day of the week to give you odds.