Yes! iOS users can completely delete their save file and start from the very beginning of NASCAR Heat Mobile.
Go to your phone settings then scroll until you find the NASCAR Heat Mobile Icon. Once you've selected the game in your settings scroll down to the very bottom and you will see the option to "Reset Save on Next Start". If you turn this on this will completely erase all game progress and you will start fresh.
*There is no option to do this for Android users.