as you may know, some sellers does not ship to China. so some chinese as like him used to register with US address. (maybe they have friend or family who live in US)
so if any seller does not ship to china, they will use US address, and otherwise, they use his China address.
and also some buyers does not bid on Chinese seller's item as they "guess" the items are bootleg or something like that.
so some chinese sellers register with US address, but the item location is China.
some russian sellers are using US / UK address with same reason.