Reset the servo horn on the steering servo. Take the horn off, put the radio trim back to center, turn the car and radio on. Then put the servo horn back on with the wheels as straight as possible. Just get the horn started on the servo, turn the car off to tighten the horn screw.

Use steering subtrim to better center steering, then set left & right endpoints. Then use steering trim as needed for final fine tuning.

Not an uncommon thing when changing radio systems.