I just sent a package to China from the US. I used Global Express USPS with tracking and confirmation and insurance. Once the package entered China the tracking completely stopped. I went to the US post office 10 days later and they were able to research it and found it was sitting unclaimed in Chinese Customs. For what that is worth to you it at least tells you that customs departments aren't too quick to communicate with USPS. My story ended good and the Chinese buyer got his 2000 dollar Rolleiflex, though I went through some nervous time.
Dennis