You cannot believe that the tracking system of the U.S., the world’s No. 1 country, the national mail carrier USPS could be worse sometimes. But, unfortunately, its true for the overseas mails arrived in the U.S. (Inbound). By the way, the past tracking records are not kept healthy. Often, they cannot retrieve the data properly when needed.
The delays may cause are related to the slow U.S. Customs inspection process at the ISCs as well.
That is for the Registered Airmail, SAL and Small Packet mail pieces sent from abroad especially. Recent experiences prove this well. Also, similar problems might be seen for the domestic mail services as many disputes available online on the serious online shopping websites.
Contrary, the tracking system works well for the International Parcel shipments!