U.S.-Chinese relations reached their nadir with the accidental bombing of the Chinese Embassy in Belgrade in May, but conditions are improving. Trade talks between the two countries resumed this week in advance of a meeting between President Clinton and Chinese President Jiang Zemin at the Asia-Pacific summit in New Zealand Sept. 12-13. Anti-U.S. propaganda, which was at a fever pitch in May and June, has evaporated and travel conditions have pretty much returned to normal.