The economic interest is the US ability to as rapidly as possible convert those shipyards to military shipyards during a large scale prolonged war. The US did not make (relatively) many ships before WW2 and then during WW2 was briefly the largest ship builder in the world.
> The economic interest is the US ability to as rapidly as possible convert those shipyards to military shipyards during a large scale prolonged war.
Nah, that doesn't add up. US needs _ships_ and SOTA military equipment to make sure that any military conflict is as short as possible (ie. US wins). Losing money on unused production capability does not make sense because in case of prolonged conflict there is time to build the capability (as it happened during WWII).
In reality, what you call "prolonged military conflict", is nothing more than normal international competition. One could even argue US is in prolonged military conflict since WWII.
In which case making rational decisions based on hard economic criteria (ie. not losing money) is the key to success.
There are no customers who want an oil tanker built in the US. Or Europe.