How bad is the USPS?

For USPS claims, either party can file a claim for damage but it's usually the receiver that files since they have the damaged part and the part and the packaging must be presented for a claim.

Only the shipper can file a claim if the item disappears.

True either can file the claim, however, they MUST have the original shipping receipt (bill of lading). Recipient isn't going to have that except under strange circumstances. Lost or damage doesn't matter with USPS, either end can file.

I used to ship almost exclusively with USPS until they screwed the pooch and stuck a fraudulent charge into my account. They say it was an error and can't remove it. I have to pay it and wait for a refund. F that... I'm not floating them a free loan because they screwed up. I use fedex small one rate boxes now for US shipping.