As a concrete example though, take a look at a recent campaign (no longer running) for Hot Pockets called Hot Pockets Dojo. We portray Japanese as nerdy, bad drivers, model minorities or disciplined loyalists. The reasons are pretty straightforward. For the most part, advertising is about us and stereotypes are the shorthand that helps us frame the hero quickly and succinctly.
In sit-coms and movies, attractive supporting characters are often given glasses, dressed down or otherwise styled to make the main character more appealing. The problem with stereotypes is they are hard to erase. So in the aftermath of a crisis or disaster when it is time to see things as they really are, we don't have a bank of reference materials to withdraw from. I watched video of homes being destroyed by a giant wave and was struck that the picture, of ranch-style houses could have been in a suburb of Seattle or San Francisco.
Advertising isn't science, manufacturing or construction. Advertising won't supply the concrete, steel or wood that will be needed to rebuild Japan. It will not contribute a single high-tech system or electronic component for a consumer electronics item. In large part, advertising is a feeder off the estimated $200 billion it will take to rebuild Japan. It can however play a significant role in destroying the monolithic portrayal of Japanese and other Asians in the media and help present a more balanced image of the fourth-largest economy in the world.