Also the implication is that Teen/Billy was driving and caused the accident that killed Wanda.
I think the implication is that Teen/Billy died in that car accident.
I’m guessing Billy Kaplan died and his body was taken over by Billy Maximoff.
Also, I’m pretty sure Teen is in the back seat. He’s not driving.
I think the Teen has been Billy Maximoff for about three years (since the end of Wandavision).
The car crash happened during WandaVision. Teen looks out the car window and sees the Hex around Westview.