I'd say Talladega is the only race track in the US I'd feel 200MPH+ speeds is achievable with a normal street legal setup without pushing things too hard, Daytona has possibilities as well. There are a few test circuits and facilities that have much larger tracks than the NASCAR ones that would probably be a better place.
I agree with the other posters, the interstates/highways are in some stretches built for speed. The biggest issue is wildlife - most tracks are fenced in, and they can keep track if anything breaks through and stop the race or testing. ON an interstate, a deer can come from no where. I've had one fly in front of me - and STOP on a deserted road twice in the short time I've been driving. I was going 35MPH...it was no problem. Almost every 944 collision I know of, involved wildlife running in front during spirited driving.
All the interstates are woods lined here, unless you are in the city - then you have traffic. Fastest I've ever gone was below 100MPH on a long bridge. Notice how I say that? I could of been doing 65MPH, 90, whatever... its dumb to give an exact speed, always say "somewhere below..."
