When considering Cayce's errors in prophecy, most people think of his earth changes prophecies. Here is a sampling of Cayce's predictions on earth changes, generally predicted to occur prior to 1998.
In 1934 Cayce said: "The earth will be broken up in many places. The early portion ('58 to '59) will see a change in the physical aspect of the west coast of America. There will be open waters to appear in the northern portions of Greenland. There will be new lands seen off the Caribbean Sea and dry land will appear...South America shall be shaken from the uppermost portion to the end..."
"Many portions of the east coast will be disturbed, as well as many portions of the west coast, as well as the central portion of the United States. In the next few years lands will appear in the Atlantic as well as the Pacific. And what is the coast line now of many a land will be the bed of an ocean...
"Portions of the now east coast of New York, or New York City itself, will in the main disappear. This will be another generation, though, here..."
"Los Angeles, San Francisco - most all of these will be among those that will be destroyed before New York even.."
"Poseidia will be among the first portions of Atlantis to rise again. Expect it in '68 and '69. Not so far away!"
(Taken from Edgar Cayce's Story of the Origin and Destiny of Man by Lytle Robinson)
I don't recall that quote about China but if I have access to the readings on CD-Rom over the weekend I'll look for it (if someone else hasn't already clarified it).
Another error, though not a prediction, from Wiki:
One of Cayce's most controversial statements[citation needed] regards the actual age of the Great Pyramid in Egypt. In one of his readings: (Q) What was the date of the actual beginning and ending of the construction of the Great Pyramid? (A) Was one hundred years in construction. Begun and completed in the period of Araaraart's time, with Atlanteans Hermes and Ra. (Q) What was the date B.C. of that period? (A) 10,490 to 10,390 before the Prince (Jesus) entered into Egypt.
In 1984, the Cayce foundation supported an effort to carbon date the pyramids of Giza. The average radiocarbon dates were 374 years earlier than expected by the Egyptologists, but nowhere near the 10,500 years B.C. claimed by Cayce.[27] The carbon dates of the Great Pyramid ranged from about 3800–2850 B.C.—about 7,000 years later than Cayce's claim