It will actually just descend.
If you pull back the throttle, you will lose a bit of speed, then this bit of speed lost will induce a slight imbalance in the longitudinal axis (which is the one going through the wings) and the nose will slightly drop, and the aircraft will establish itself in a descent at the same speed as your previous cruise.
Because you're basically trimming for a speed (or rather, an AoA, which is almost equivalent on the short term)
Of course if you transition sharply from 100% power cruise (that's forbidden but imagine) to feathering propeller, you'll see more speed lost, but the idea is the same, you'll still transition to a descent. And you won't stall.
Let's keep it that simple for now.
Stalling is by definition the moment when the air is no longer able to stick to the airfoil's shape. It will occur only at one AoA in normal conditions of flying for you piper warrior.
However, if you change the Reynolds number or Mach number your critical AoA could change significantly
For instance if you fly an Airbus at high mach numbers, your critical aoa will drastically reduce.
If you tried to build an airplane for ants, you would have a very different Reynolds number and this would lead to a different critical AoA even while keeping the same airplane and airfoil shape.
To sum it up simply --> your piper warrior always stalls at the same AoA, given constant flaps configuration