Americans are major owners of foreign flag ships, among the top 5 shipowning nationalities. Shipowners, a great many of whom are US based Americans, operate foreign built ships under foreign flags, with foreign crews that conduct trade with the US.
These American shipowners could, if they wished to, reflag their foreign built ships under the US flag and hire American officers and crew. Nothing prevents that, certainly not the Jones Act.
American shipowners invented “flags of convenience” decades ago to avoid US taxes, and US safety regulations. Initially, they employed a lot of American officers, however, Americans were eventually replaced by very low wage foreign officers.
Investment capital flows to the least regulated, lowest cost, and highest profit opportunities. As long as Americans are allowed to own and operate ships under lower cost flags of convenience, they will do so.