Government/environment regulation, population density, lean manufacturing, outsourcing, offshoring, automation, shipping, fuel/transportation costs, infrastructure, proximity to skilled labor pools, etc.
There's no one thing killing the rust belt jobs. There is no simple solution. Regulation is one contributing factor, to be sure. I'm always a big believer that any non-safety related regulation should be on a reasonable sliding scale. That said, even if all regulatory costs magically became zero, it wouldn't necessarily completely change the rust belt. Hell, we're still near the top of manufacturing in the entire world. Automation is just reducing the number of workers needed. What's left is skilled labor. That near universally need to be acquired by the worker in question.
Sadly, same as Millcreek, I'm not seeing anything that anyone could realistically do that will change ALL of the equations.
I'm also very aware that city workers largely flat out openly hate and despise people not in urban areas.