Cessna 172 instructor pilot reported an inflight upset and loss of control incident from an A320 on approach to SNA airport. Control was regained at low altitude; narrowly averting a collision with a taxiing B737NG.

Narrative

Conducting continuous left closed traffic operations on Runway 20L SNA in a Cessna 172S with myself sitting left seat and student sitting right seat as they are training for CFI. An Airbus A320 was landing on the parallel Runway 20R and was advised to maintain visible separation and caution wake turbulence from SNA tower 119.9 for that Airbus. We accepted and were cleared for the option Runway 20L. Airbus A320 continued to land and made it to Runway 20R while we were turning base to final Runway 20L. We altered our flight path to remain above that of the Airbus as winds were reported and observed to be a right crosswind. Meanwhile a B737 moved forward to cross Runway 20L and hold short 20R on Lima. This reaffirmed our decision to remain high to avoid jet blast as well as the landing Airbus's wake. Continuing the descent to land; stable and configured; aircraft encountered the onset of wake turbulence forces and began to roll right uncommanded directly above 20L runway threshold at approximately 75-100 ft. AGL. I instructed the student to immediately initiate a go-around to which there was a delayed reaction; within 1-2 seconds after command was given; aircraft encountered substantially stronger wake turbulence forces and abruptly rolled uncommanded to the right departing controlled flight rolling to approximately 40+ degrees of bank and -10+ degrees of nose pitch down. With student's delayed reaction to go-around I commanded 'my controls' which were not relinquished causing me to forcefully take the controls with continuous verbal command given in a raised voice. With forceful takeover of the controls; immediate full power was commanded and began to maneuver to avoid contacting the ground and the B737 holding between the runways on L. Aircraft was on a collision course with the B737's left wing section which was narrowly avoided after regaining controlled flight by a margin of 20-50 ft. from the B737 and 15-30 ft. from the ground. After successful maneuvering to avoid collision; continued a recovery and climb back towards Runway 20L center line as the aircraft made it roughly to location of the Runway 20R PAPIs at its furthest deviation. John Wayne Tower was then advised of the go-around and presence of severe wake turbulence event. Tower acknowledged and was startled as well as they witnessed the occurrence and asked if we request any assistance. Advised we did not require assistance and no aircraft damage was observed followed by requesting to terminate. Flight was terminated; returned to parking and assessed for any damage. None observed.