If Indy and NASCAR ceased to exist tomorrow, I guarantee you that F1 would gain rapid popularity in the States and 2-3 American drivers would pop up and be successful. Theres just too much competition among "big-time" racing series in America.
Wait a few more decades. From the articles I've read over the past couple years, NASCAR viewership is still more or less consistent (sometimes higher, sometimes lower, but over the big picture remain essentially the same) over the past decades, but they're basically steady with their older demographics. Amongst younger audiences, NASCAR is way down. I have theories as to why they've lost interest amongst younger viewers, but they aren't relevant here.
Now, those older fans won't live forever. Over the coming years they'll gradually die off, eventually at a rate that far exceeds the new younger viewers that are coming onboard. So, given enough time, NASCAR should find itself a dim shadow of its former self. That just leaves us with IndyCar, which has but a small fraction of NASCAR's popularity, and it isn't increasing. In fact, while it did temporarily improve with the arrival of "Danica Mania" some time back, that gradually petered back out.
If the current trends continue over the next couple decades, NASCAR should have far more limited presence than it does now, and IndyCar is just barely here anyway, so the time may come that F1 is a more realistic prospect for American racers.
Who know who had a name made for F1? Scott Speed. Too bad he didn't live up to his name.
Yeah, I always thought it was an awesome driver name wasted. It's made for racing, like "Gale Weathers" would be perfect for a meteorologist.