Yes rubbing alcohol can damage car paint when used at full strength.
Although the rubbing alcohol you buy in stores is diluted some with water you should dilute it just a bit more with some water before you use the rubbing alcohol on the car paint.
I've used some diluted rubbing alcohol to get tree sap off my car paint and it never damaged the car paint.
But I once tried undiluted rubbing alcohol and it removed some of the car paint.
So dilute the rubbing alcohol a bit before applying the rubbing alcohol to the car to avoid damaging the car paint.
If you have some tree sap on the car itself then using some WD 40 or mineral spirits on the car paint will remove the tree sap from the car without damaging the car paint.
You can use rubbing alcohol or acetone based nail polish remover to remove tree sap from windshields as well.