Also, on the Florida side, Jacksonville port has the CSX, Norfolk & Southern, and a coastline local railroad that runs down into Florida. Plus, I-95, I-10, and access to US 82 to I-75. Can get to all the southeast in 1 day, most of the eastern half of the country in 2 days.
I think that the availability of offloading capacity outweighs the cost of traveling through the Panama Canal to the east coast and gulf. Plus, it eases pressure on the west coast ports.
That's the Florida East Coast, a short line that reaches to the Port of Miami via a connection opened only a few years ago. Its Jacksonville port to Miami port connection is more direct than CSX.
FYI most of those container ships are larger than one of our super aircraft carriers——100K to 200,000 tons——they just wont wedge thru the Panama canal. Our carriers can go thru but only if the canal guys lay down their light poles.
Who owns the Canal now?
Houston, New Orleans, Mobile, maybe Pensacola and Tampa could all take ships.