EMS is treated by the USPS as an express mail piece when it arrives in the USA. It needs to be signed for, and it should be delivered by a special postal courier separate, and earlier in the day than your regular postman.
In mail sorting centers, EMS is given priority over other mail, since it is special courier mail.
That is why you have a problem here ... EMS should be at your home the day after it leaves Customs.
Altho Im sure nothing is seriously wrong, the PO is screwing up big time by not delivering this piece immediately.
Normally I see EMS in 1 day out of Customs but once, it took 9 days. I assume someone dropped the box in the back of their truck and found it 9 days later.