Yes, without the USPS lots of people would have to drive into the nearest town to get anything, and presumably letters would become completely cost-prohibitive

Yes, without the USPS lots of people would have to drive into the nearest town to get anything, and presumably letters would become completely cost-prohibitive to send even to people in cities. But even setting these things aside, USPS is almost always a better experience as either sender or receiver than any of the other competitors in the US.