I've read that it has to do with the Age of Exploration and the influx of spices into Europe. What I read basically said that heavily seasoned food was seen as a manifestation of hedonism and for that reason groups like the Puritans avoided them and then that influenced American foodways. A number of spices are also thought to be aphrodisiacs, or at least to promote blood circulation, like garlic and chili peppers.
The New Yorker had an excellent piece a while back examining the zany world that is competitive chili growing. There's definitely an interesting relationship between spice and masculinity/virility:
"Chiliheads are mostly American, British, and Australian guys. (There is also a valiant Scandinavian contingent.) Chili growing is to gardening as grilling is to cooking, allowing men to enter, and dominate, a domestic sphere without sacrificing their bluster."