I never have any items directly from USPS with tracking info, so I didn't bother checking. But the items usually comes in after 3-5 weeks. That's why I'd rather use third party forwarding service like comGateway

If you have tracking number, usually it'll update to reflect the hold up by customs. Last time, I ordered a pen and since it's a pen, I didn't waste any money to pay extra for tracking. After a month, I check my eBay list of bought items, I realized that the item is not arrive yet. I contacted the seller and he said the item was returned to him. He posted a picture with customs stamp saying "Tidak dituntut". So to be on the safe side, just go and check by yourself.

That would be sufficient