So if someone says "national security" is above economic interest of US, I would say these people mean _their_ economic interest is above economic interest of US and use both terms as a cover.
There are clear national security reasons for the government to prop up shipbuilding and semiconductors.
Are you saying countries without shipbuilding facilities or not producing semicondutors are being conquered and their citizens being slaughtered?
I'd say that is fear mongering done by the people doing business on "national security".
Yes that is a clear risk. For most of human history, powerful leaders have unleashed violence on their neighbors to increase their wealth and prestige. For about 70 years, the cold war balance prevented very catastrophic wars between powerful nations but we now seem to be having an atavistic throw back of powerful nations being led by expansionist leaders. You either need to create your own manufacturing capacity or be at the mercy of others.
The United States is the greatest power the world has ever seen. While the oceans protect us, the truth is that even the White House was once burned down in a war.
There are no customers who want an oil tanker built in the US. Or Europe.
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.