The bit I can't get my head around, is the forces in the turn. The Super Cub at ZERO groundspeed has NO momentum to overcome. Here centrifugal/centripetal forces don't apply. Therefore, with the aircraft banked, the horizontal component of the total reaction is unbalanced!!!
Only for an instant. An unbalanced force implies an acceleration - so the instant it banks it also begins a turn and the balance is restored.
Remember that acceleration is changing velocity. Velocity has speed and direction components. Therefore even turning at a constant speed implies an acceleration.