The Jones Act is the reason there is such low utilization of the waterways that are one of the most valuable geographic treasures of North America. There is good reason to ship between US cities where it can be done, it can presently be done for about 1/3 the cost of rail, and 1/5 the cost of truck.[1]
A repeal of the Jones act would help reduce the wear and tear on our highways and railways. It would lower overall costs, and reduce greenhouse emissions. There are also economies of scale that would likely kick in with increased shipping.
Valuable for how long, though? With the hydrological cycle changing and causing deluges in places and drought in others, those waterways might not be navigable in 50 years.