Not dead, but very dormant. And that can lead to problems. If heavy industry came back to my neck of the woods (a rust-belt state), it would soon be followed by union organizers demanding all sorts of things.
At first, workers might put the union at arm's length, as they would be happy to just have a job. But in a few years the seductive promises of a union would start to have an effect.
And that would be no big deal, if the laws provided for a level management-union playing field. As in: Workers should have every freedom to join a union. Management should have every freedom to refuse to talk to a union, and permanently fire strikers. See who blinks first.
The south would be the place for resurgent manufacturing. At lest that is how I see it.