Here is a call to the eBay API to find items by EAN (similiar to UPC):
Notice that it doesn't find any items. But when I manually go to http://www.ebay.co.uk and search for the term "5050582929393", items show up. In fact, even one of the items has the EAN field filled with 5050582929393.
How can I make sure the API is calling for items worldwide???