Alignment

There is a lot more to wheel alignment than just being in spec. The specs have a lot of tolerance and can still favor one side or the other. That being said, the road you drive on has a lot to do with how it drives. Nearly all roads are crowned to the right and there is a normal tendency for the car to follow the crown. For this reason many alignment techs will pack a little bit of left pull into it to help compensate for that but there is no setting that will work on all roads.

The other possibility is the tires are causing the pull which is also quite common. The way to determine that is to cross the front tires left to right and right to left and see what the car does then. If the pull changes, the tires are the problem.