Pretty much the only American that has a shot to break the jinx is Susan Dunklee in the Womens 7.5km Sprint. She is currently at around the 14-1 mark to win a medal in that event.
Biathletes could very well be the fittest athletes on the planet, that sport is brutal, unreal how fit you have to be to do that sport. And you have to bring your heart rate and breathing down to shoot the targets, that ain't easy at all.