1. This is the tracking I found for your parcel:
Number: LT208617837CN
Package Status: In Transit
Destination Country: United States
2016-09-25 14:09 Origin Post is Preparing Shipment, We have received notice that the originating post is preparing to dispatch this mail piece.
2016-09-25 14:09 CHINA, SHANGHAI EMS, Processed Through Facility
2016-09-23 23:02 CHINA, Acceptance
Origin Country: China
2016-09-25 23:33 In Shanghai, left Shanghai Pudong airport
2016-09-25 23:33 Shanghai City and leave Shanghai to Chicago
2016-09-23 23:02 Shanghai, express delivery of bulk acceptance has been received (the embrace cast member name: 01, phone:)
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2. And this tracking:
International Mail# LT208617837CN Tracking Result
Summary
Tracking number Origin Destination Status
LT208617837CN CHINA UNITED STATES On route

History Detail
Local date/time Activity Location Remarks
23-Sep-2016 23:02 Received by Post Office 200888
25-Sep-2016 14:09 Departure export customs SHANGHAI EMS

3. Your parcel is what we call E Packet parcel and normally it take from 6 to 12 working days to be deliver, this number of days exclude the time the parcel is spending in the Customs Office in China and USA. According to the above tracking your parcel departed China for Chicago.

4. I don't see anything wrong in the tracking and I suspect that you should see some movement next week on the USPS site.

Hope this help.