America is where most of the big boys are because most of them like to race illegally. It is true that won't prove a thing, but in this country, you need to race illegally or you will be left out. Besides, some there are rewards that you can get based on the position that you got in the race.
Drive your car as fast as possible till you reach the finish line. Regardless of your position, you are getting part of the reward money. You can use it to upgrade your car as you will be needing it later. Once, you got one of the top three position then you can unlock a new race.