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.
They do now, but it’s hard to start on a small scale. How can you say there was no demand in the US when the barriers to entry in the US market were so high?
The hovercraft I was on was between Bolivia and Peru on Lake Titkaka at abou 13,000 feet. They had less than a handful of the boats. I don’t see how setting up a manufacturing subsidiary in the US is efficient for such small numbers. There was a subsidiary set up for building hovercraft based amphibious landing craft so the US Navy could land Marines on beaches, but it didn’t make any boats for civilian use in the US.