This game confuses me so much. But all I want is the Mustang, and judging by the walkthroughs and unlockables section, I am not going in order. I know you unlock cars by beating the URL races, but I can't get any more. Heck, I can't get any races at all on my map. Do I have to go around looking for outruns and random races or is my game messed up?
I think Link dropped something on the way over to Twilight Princess. The only thing more fun than flying is blowing stuff up while flying.
Have you finished all of your required sponsor races?
If you're one or two races, and one URL race, away from completing your contract, look for hidden races. They don't show on the map, there's almost always one or more available, and as an added bonus, they pay very, very well.