There are 118,000 ships in the world. Only 115 are US flagged.
Blame politicians and unions.
Blame eco-nuts who would punish U.S. companies with U.S. “environmental laws” - because of the exhaust from the giant, very-high torque, very low RPM, diesel engines.
The foreign flags - thru a maze of international “free trade” agreements - get away with using low-priced fuel (low, because of the quality of the oil, also being low) that have high carbon emissions . . . for the high seas legs of very heavy transportation.
That the public generally does not know about; as the public gets the bill from the eco-nuts, because the public “must compensate” for the container ship emissions, by being forced to use EV’s.