Talk politics.

I don't know... My assumption is that USPS mail revenue from more populated areas helps balance out low revenues or deficits from rural areas. Private companies wouldn't have to serve rural areas, so they could avoid those and just focus on the high revenue areas. That might cut into USPS profits, which would cause them to raise prices overall to offset the rural low revenues/losses. The USPS would compete, but it wouldn't be on an even playing field.