Imagine if they had to pre pay pensions and the VA - they'd be insanely underwater.
Indirectly it is.
Depending on how you measure externalities, it probably is
They're not measuring externalities with the Postal Service.
Also giving subsidy to ups and fedex for all the unprofitable rural / low density routes to keep it available in rural areas will probably end costing more
I dunno. There are some areas (speaking from experience unfortunately) where UPS and Fedex deliver but USPS doesn't.