It will definitely help some US businesses and will definitely hurt others. The same way import tariffs on steel are good for US steel companies, they are hurting the US companies who are using that US steel in their products.
And that's without taking retaliation tariffs into account.
Self-sufficiency has a cost, to be sure. But it also has value. Same as with foreign dependence -- we are re-learning that foreign dependency has downsides.
The rebuilding of America's industry is the inverse of the pain experienced during the tearing down of these industries during the American industrial bloodletting of the 1970s, when production was sent "overseas" (primarily China).
For GenX and younger, it's almost difficult to appreciate that America built almost everything it needed (including electronic components), and was the best in the world, 50 short years ago. One could open up a television or an automobile, and every component was made here. Now it is quite impossible because we have surrendered certain industries.
It hurts the US companies until they go back to using higher-quality US steel, which they should have been doing in the first place.
Chinese steel is of such low quality that, after wastage is accounted for, you essentially end up paying just as much as you would have for US steel. The companies that save on Chinese steel are just passing on the externalities to their customers.
Hmm...let's see. I know absolutely nothing about the quality of US-vs-Chinese steel but, assuming everything you say is true, that means companies buying steel are perfectly fine buying low quality steel. And they will be perfectly fine buying low quality steel, regardless of where the supplier is located. So, what will inevitably follow is that US steel manufacturers will lower the quality of their steel to match Chinese's, while keeping the price high. The result - US consumers paying more for the same shitty quality steel.