Aside from Mario Andretti (who could drive anything) and Jacques Villeneuve I can't recall any CART/CHAMP CAR/ INDY CAR drivers who managed to make even a brief ripple in Formula 1, and that goes back to 1950.
Rick Mears tested a Brabham and impressed, however he was unimpressed by the amount of money HE was expected to bring, that was a shame.
Michael Andretti actually put in a few decent drives but screwed up by attempting to commute between the US and the UK, while his 'unfortunate' wife at the time made life uncomfortable for him within McLaren.
Paul Tracey and Al Unser Jr. both tested for Benetton and failed to impress. IIRC Geoff Gordon ran a brief test and did make quite an impression but decided the NASCAR money and the lifestyle appealed more than F1.
Taking a leap back in time and despite being genuine 'Racers', Jim Hall, Dan Gurney, Masten Gregory, Hap Sharp, Bobby Unser, Chuck Daigh, Mark O'Donohue and several other names that escape me failed to make the cut, despite all being stick and pedal drivers as well as including several outstanding engineers.
While Phil Hill won a World Drivers Championship I can't remember him driving the NASCAR circuits at all, he was however and outstanding World Sportscar driver and quite the 'Ace' in the SCCA and CanAm series.
At the present it is impossible to compare NASCAR and Formula 1 without laughing at the stupidity of the way both are conducted, along with the 'Celebrity' promotion status of far too many 'drivers'.
Both need the management to be removed, better still, terminated with extreme prejudice ........
