1st off scca auto x events do require you to register with the scca. once registered you can bring whatever you like out there to auto x as long as its safe. as for auto x and road racing being mostly for imports that can be further from the truth. there are usually a good amount of car both domestic and import. when i lived in jax there was this older guy that was paralyzed from the waist down and he was racing a specially made c5 vette. heck he would even change his road tires to slicks when he got out there all by himself.

i would strongly suggest starting with learning your basic car control with autocrossing before moving on to road racing. as for drifting, yea i guess its kinda cool to see but i think you end up spending more money drifting than autocrossing or road racing. that and you get alot more time out of your tires.

as for any aspirations of becoming a professional driver, good luck. most of them start racing before they have a license.