Adding to the previous reply, consider that virtually all swept wings are also tapered - the thinner airfoil section and reduced planform area at the tip both contribute to a higher local stall speed at the tip.
Another large contributor to the stall onset location is the upwash from air flowing around the fuselage from bottom to top (at a positive AOA). In the wing root area, this upwash increases the local AOA substantially, although propwash often mitigates this somewhat in prop aircraft.
Finally, it's worth remembering that most GA aircraft have a few degrees of washout built into the wing, meaning that the the wing is gradually curved (nose-downward) from the root to the tip to mitigate tip stalls and the resulting roll tendencies.