I first became aware of th Jones Act back in the late 70’s when I found out that the reason there were no hovercraft operating in the US, because the were none built in the US. Only US built ships are allowed to operate between US ports without a stop in a foreign port in between. I thought it was stupid to protect a lazy industry that didn’t want improve its products.
BMW , Honda, Toyota all build cars here in the US.
If there is no supply-demand for hovercraft manufacturers to set up shop here, it’s cuz there might not be a market for HC ships - kind of like limited markets for high speed trains.