Americans long have leavened their powerful global image with goofiness, a cheerful confidence that can deflect international wonder over certain strains of ignorance into a smile. Behold, for example, the cheesehead hat. Made of sofa foam and sunny yellow defiance, the hat was created in the late 1980s in response to the taunting faced by supporters of sports teams in Wisconsin, which has long called itself America’s dairyland. “Cheeseheads!” residents of neighboring Illinois said. The insult