with that out of way, what you should do it to have the US court order certified in a Middle level people's court, the order then will be enforced at the local court...
my suggestion to you is to retain an attorney in China, and have that person deal with the matter...China's rule is very loose, Chinese attorney will provide contigent fee service ranging from 5 to 30% dependent upon if you pay the court fee or the attorney take care of all the expense...
Personally, I think that IF you have the right connection, i.e., if you hire the right attorney, as long as your ex has property, almost for sure you will get it...again, let me emphsize, you must have a well-connected attorney in China..
good luck.