U.S. video game companies haven’t done well in China. Stymied by piracy and sometimes unable to understand the tastes of Chinese gamers, they’re floundering in one of the fastest-growing game markets. But Seattle-based PopCap Games, which has pioneered the development of casual games such as “Bejeweled,†hopes to buck the trend. The company is sending its long-time business development director James Gwertzman to Shanghai to head the company’s Asia/Pacific office. Gwertzman has studied the Chi