It'll obviously be industry dependent.

A few that I'd see the need.

- Railroads - The lines themselves and the operation should be owned by the federal government. Private rail companies should buy access which pays for line expansion and maintenance. The US needs regulations on things like train length and line speeds (none of these super massive trains blocking roadways because they don't fit inside a rail yard).

- Medicine - Medicare for all, but honestly I think nationalizing major hospitals and pharmaceuticals would probably be warranted. It's in the national interest to fund a wide breadth of research and medicine production even if that medicine doesn't ultimately turn a profit. But even if we just did insurance, the US is already covering the most expensive pool of individuals with Medicare (old people) expanding it to all citizens wouldn't be that expensive. Reform to medicare would help (particularly removing Part C, that's just a slush fund for insurance companies, but then also expanding and simplifying the other parts).

Utilities ownership - Doesn't need to be nationalized, but having municipal or state ran utilities would, IMO, be preferable. The state utilities boards suck and putting in checks for utility companies. They aren't elected and are easy to corrupt. For example, my water utility was recently purchased by a company. In order to cover the loan they took out to purchase the previous water company, they raised rates (fat chance those go down). For telecommunications, I think a British telecom style system would work well. The government owns the lines while various telecommunication companies compete for service. That'd make it easier for more than just 2 companies providing internet service to a given location. Cellular networks practically already work like this, the big 3 own everything and sub-carriers just lease access. It'd be better if the government nationally owned cell service deployment. Especially in terms of spectrum usage.

- Food production - I don't really think government ownership is needed here, I think anti-trust and breakups are needed. These markets have consolidated to a huge extent which is really bad for everyone. Having just ~5 different national grocers is a bad thing. Having just a few mills (like general mills) is a bad thing.

- Chip fabrication - This should be owned by the government much like TSMC. And like TSMC, the likes of nvidia/intel/amd can buy a fab to do their runs. Fabs are just too crazy expensive and losing the competitive edge here is a security problem.

Basically, my view centers mostly around when an industry gets too consolidated. Especially when I think it's something that has critical importance to the general public. I could be open to more of these sorts of actions, it just depends on if an industry can be naturally competitive or not. Like, for example, I think a nationalized shoe manufacturing is a dumb idea as it's already a highly competitive market that could be easily broken up.

Hopefully that answers your question.