That's like comparing Pirates of the Caribbean and it's a small world. :shrug:
Though having similar ride systems and taking place in cars, the similarities end about there. Look at all of the construction working being done now at DCA and compare that to the construction that was done to work on Test Track. While Test Track is an e-ticket mostly because of the thrills, Radiator Springs Racers is attempting to be an e-ticket on all levels, including immersion. It'll have cars racing side-by-side, past waterfalls, through curves, past ride scenes, and will have re-rideability.
That said, it's been posted numerous times here by several reputable posters that there are proposals to put a Carsland (or some variation thereof) at the MGM Studios, replacing the Backlot Tour and that area.