according to the Mattis, us military interests only account for about 3% of steel produced in the US, so I think we are pretty far from needing foreign nations to build ships, at least for the steel.
I'm not sure we'll need steel after a major war between super powers, we haven't had one in 70 years. Even if we need more steel, we can always ramp up production, or import steel, like we did in Iraq to up armor the HMMVW. We are making as much steel today as we did at the end of WW2, and there's no doubt we'll need less physical hardware in any future conflict. More domestic steel production now, doesn't appear to affect national security.