After you file

You can try to do the following to delete your state amended return:

If you are using TurboTax Online:

1. Sign in to TurboTax and open your return by selecting Continue or Pick up where you left off.
2. In the left menu, select Tax Tools and then Tools.
3. In the pop-up window Tool Center, choose Delete a form.
4. Select Delete next to the amended form for the state. 

If you are using TurboTax Desktop:

1. Open your return.
2. Switch to Forms mode.
3. In the left pane, select your state amended form and select "Delete"
4. Follow the prompts

@michinori-kaneko