Parcel diverted and in customs

[Khyber]

Hello,
A badge sent for me by Royal Mail to India has wrongly been sent to the US via USPS ..On 19th it showed arrived at Chicago and the next day that it was on way to destination .so I presumed it was rerouted to the UK or India, but today I see a message that says inbound with US customs.
Why does it have to go through US customs and what is likely to happen next? How soon does US customs clear packages and will they realise the mistake at that stage and send it back?
I had a similar thing happening a couple of years back and it was rerouted safely though it was delayed by a couple of weeks, but I don't recall it being sent to customs..

I guess I'll jsut have to wait and watch but can anyone tell me how this works in the US.