Barber Motorsports Park, Birmingham Alabama.
WIKI
This track is just great, plenty of elevation changes. Not to mention it's a newer track, being opened in 2003. The Circuit is 2.3 Miles or 3.7 Kilometers long. The track has plenty of room to run off and not stuff it in a wall. Though it's not astro turf or asphalt run off, well some is asphalt. The IRL will be racing here in 2010, the Grand Am series already visits.
The track record for a Daytona Prototype is 1:20:613 by Max Papis in a Ganassi racing DP. I think F1 would lap the circuit with sub 60 second laps perhaps, how much I'm really not sure. The unofficial lap record is 1:09:XXX for a Dalara-Honda IRL car, set by Will Power.
Lapping Barber on board a Radical SR3.
This place seems like it would fit with the European tracks on the schedule, yet has more character than the newer F1 tracks, just lacking in the length department. As I said, the elevation changes are great. Not to mention I'd be able to drive up there in under 9 hours. I really think this track would do the USGP justice, more so than a roval, I really don't like Indy, not one bit.
Does it have F1 level facilitys? No probably not, the paddock may need to be larger, can't be working on cars out in that southern heat

.
Does it have the runoff? Yes, but they like it to be paved.
Will the front the fees to have F1 show up? Highly unlikely.
Would it be a great track to run the USGP on? YES! (IMO)