In 1968, the United States started what is now a long history of providing protections to the US steel industry from competition from foreign steel manufacturers. There have been several bans on steel imports which allow the US steel industry to charge higher prices.
And because their jobs have been made easier by these import bans and not having to compete with foreign steel at lower prices, the industry has stagnated. The Heritage Foundation reported by that industry hadn't modernized in ways that would keep it competitive. Why should they? Their place in the our markets is protected.
Who does this hurt? It's not just foreign steel producers, humans we presumably don't care about when it comes to the US economy. But it also hurts American producers of other products that use steel produced in America. It makes steel more expensive for them, which makes their products (including American-made cars we're constantly told we should be buying) more expensive.