[DoodleDawg]

Why does Boeing have a contract for their starliner? Did you see how they tried to stop SpaceX with their government influence?

Stupid analogies aside, if the southern colonies had established a ship-building industry or had run their own shipping lines then there is no reason why they would not have been in a position to compete with northern colonies and, after independence, gotten their own share of mail contracts. Yet there were no colonial shipbuilders or colonial shipping lines in the south. I suppose the northern colonies conspired with the King to undermine all the attempts to establish them? Or some similar conspiracy theory from your fertile imagination?

[DiogenesLamp]

...if the southern colonies had established a ship-building industry...

According to the Registry Entry, "The Horizon" had the following characteristics.

It was a "Ship" as distinguished from other naval vessels, such as a sloop or a brig.
It's Master was a man named "H. White".
It was 310 feet long in 1801. It was Single Deck with Beams.
It was Manufactured in Charleston South Carolina.
It was sheathed with copper over boards.
It was 1 year old when it was inspected by Llyod's.
It's original Owner was a man named "Mackler" and apparently Co-Owned by a man named "McClure."(edit: I have since come to believe that "Mackler" is merely "McClure" misspelled.)
It draughted 16 feet when heavily loaded.
It's Ports of survey were London and St. Vincent.
It's condition (at time of examination) was classified "A-1".

Yet there were no colonial shipbuilders or colonial shipping lines in the south.

Clearly you are mistaken.