Have you checked that EMS tracking number at USPS? Typically there is a hand-off after the shipment clears customs. Also, typically at least a week goes by from the time EMS gets the shipment until new info shows on the tracking ID.
So far, everything I've ordered from XMIplay has only taken no more than 10 business days to travel from China to Atlanta, once I have a tracking number.
Seems Flyxii has done their part if they sent you a tracking number so now all you can do is wait. I've also seen shipments slow down after Xmas due to the overall lack of shipments in January and maybe lots of people in the shipping business take vacation after the holidays, not sure which.