Well there is IROC-the International Race Of Champions. Just what you suggest but in a NASCAR type car running about ten events a year. It has deteriorated in recent years and I don't even know if it is still run.
Roger Penske originated the series in the mid-70's with top drivers from every major series around the world in equally prepped Porsche 911 RSR's. In it's last few years it primarily featured American Stock Car, Indy and Outlaw class drivers with a few notable Sports Car drivers from time to time.
It was great racing in it's heyday but developed a NASCAR-Lites feel by the 90's.
Heaven: Where the cooks are French, the police are British, the lovers are Greek, the mechanics are German, and it is all organized by the Swiss.
Hell: Where the cooks are British, the police are German, the lovers are Swiss, the mechanics are French, and it is all organized by the Greeks.