And is getting called out on it.
See Brad, there are significantly fewer F1 rides (24) than Cup rides (43+) available. Two, neither can make a definitive claim since, as Jenna Fryer pointed out, they're two totally different animals. Most (though not all) US racers grow up on the stock car ladder and formula. Most European/Int'l drivers grow up on the formula car ladder and formula. They just never meet in neutral circumstances to show who is "best."
Further, why would a top NASCAR guy seriously try F1? It makes no business sense. NASCAR guys do quite well financially thank you very much. Setting aside skill sets, that alone is a huge reason why you'll never see crossover. And, in fairness, the F1 teams, out of arrogance and the whole "skill set" thing, would never seriously consider an American Cup driver. That does NOT, however, mean Cup guys are superior to F1 driverd.