This could be good.
To improve on what you have already, I would do the following.
1) Improve the sound quality of the car.
2) Add a couple more songs to the list and add a mute option as well.
3) At the moment, the graphics of the game are a bit dull.
All the enemy cars are identical in shape and colour.
Give the enemy cars some more colours (except for red of course), and perhaps even make a few different styles of car.
4) Change the distance from miles to metres.
5) The game is pretty hard. There should be maybe 3 or 4 difficulty levels to choose from (the game as it is now, would be at hard level).
6) Maybe add an arcade mode with 10 or so stages, where the user has to make it to a certain distance before the car crashes.
7) Give the user more lives (maybe 3). At the moment the game only lasts a few seconds.
8) Add a high-scores table.
9) Finally, add some music to the 'Game Over' section.
Well that is all from me. Good luck with everything, and if you take this all on board, I'm certain you'll create a very popular game :).