There certainly IS a quite a bit of competitive road racing in the states: American LeMans, Formula Atlantic, GT, SCCA to name a few. Even CART and NASCAR have their share: Sears Point, Laguna Seca, Mid Ohio, Watkins Glen. It just seems that the majority of US race fans (including some of the posters in this thread) choose not to pay any attention...
Regarding an American driver in F1, Red Bull is sponsoring a "talent search" program, spear-headed by former F1 pilot Danny Sullivan, to find a driver who they feel has both the ability, talent and character to compete at the F1 level. I believe that the chosen one would end up with a F3000 drive as the next logical step.
Finally, F1 drivers are treated as bonified sports superstars in there respective countries and, for the most part, everywhere except the US. These guys are certainly not "robots" who simply drive for their team. As a matter of fact, they are probably the most egotistical sporting personalities on the planet. Both Michael Jordan and Michael Schumacher are equally as popular outside the US.