I’m not sure why you think protectionism (by the local government) can’t kill an industry. It happened to American steel as well: the American steel industry was “protected” while foreign steel companies innovated their production processes.
The timeline goes like this:
1. Government gets pressured by industry to protect domestic industry from outside competition
2. Domestic industry stagnates as it has no reason to make competitive products
3. Time passes, quality/value gulf becomes so large that it becomes impossible to catch up to competition. It becomes impossible to export your goods and even domestic customers look elsewhere.
If the USA dropped tariffs and bans against Chinese car companies, American car companies would need to improve rapidly to survive. Instead, they’re selling us $50,000 decade old dinosaur designs like the Chrysler Pacifica.
This literally already happened to them with Japanese cars. And let me tell you, you don’t want to drive a Chevrolet from before Honda and Toyota sold cars in the United States.
Not protectionism related, but look at the MacBook Neo competitors shown off by Dell and HP at Computex. Competition drives innovation and cost reduction for consumers. Apple forced HP and Dell to make an affordable aluminum chassis computer for the masses and consumers are the winner in the situation.
It's also said to be one of the ironic long term impacts of the Jones Act (of 1920) in the US. The Jones Act among other things requires all US flagged ships at sea to be manufactured in the US in a hope to protect US manufacturing of ships, but instead in practice just became that most non-military ships just aren't officially flagged as US ships ever. For instance there's generally only one or two US flagged cruise ships in existence in a given year, they get US flagged through manufacturing loopholes (primarily constructed where other cruise ships are, but with enough "finishing touches" in the US to count as US manufactured), are smaller than the average cruise ship, and mostly only exist for Hawaiian island hopping cruises. (This is due to another quirk in the Jones Act that ships traveling directly between two US ports need to be US flagged. Most cruises can easily stop at a non-US port in between US ports, such as various Canadian, Mexican, and many Caribbean island ports, but from Hawaii the next non-US ports can be quite a bit more travel time and traveling to Tahiti and back just to see two different Hawaiian islands can be a bit much.)
Since the closure of Jeffboat in 2018 (among others), there's no non-military ship manufacturers in the US for anything even resembling cruise ship size (and even before that manufacturers like Jeffboat were mostly only making cargo barges) and the US military contractors have basically shrunk to a duopoly. Probably not the 100+ years later expectations of the Jones Act authors.