Last year, China's annual spending on e-commerce shot past the US, and the gap is widening. It grew 50% last year, to just short of $450 billion annually. This compares to a total ecommerce spend of $262.5 billion in the US. Astonishing figures. That $450 billion spent online is out of a total of around $3.8 trillion, spent on retail in that country, according to China's National Bureau of Statistics. (Their site, in Mandarin, is here.)
For a variety of reasons, most US retailers do not sell to China: shipping, payments, customs, complexity, and certainly fraud. They simply don't have a reliable way to validate that the person paying for goods online is truly the holder of the card.
More details are here at Internet Retailer.