Stamina isn't a terrible argument, NFL players wouldn't cope in Rugby. Not to mention Rugby is a lot more physical than NFL. If you want to talk which is the more manlier sport, Rugby. The more physically demanding sport, Rugby. The more tactically astute sport, NFL. The more explosive sport, NFL.
The Americans put on a good show, cheerleaders 'n' confetti. You have to wait for plays, so I can see where you'd get the excitement and tension from. But I'd rather watch a game of Rugby, NFL is good in a 30 second clip.
I do love the 'If America cared...' argument, it holds no merit but it's used as if it does. It also seems the only sports they don't care about are the ones that actually matter outside of the country.