You're going from PHL - ORD - CHA - and then back to ORD ???
If you're just doing PHL-ORD-HKG, then yes, AA should be able to thru check you all the way to HKG. And at ORD, CX agents will pull your bag out and stick a proper priority tag on your bag too !
Next time, book it as one ticket - it is possible, you know ..