A couple of additions and caveats.

Friend of mine at ORNL has been talking up compressed air energy storage (CAES). I'm somewhat dubious due to the Boyles law heating/cooling problem (gasses heat when compressed, cool when expanded, and the resulting heat flows affect both efficiency and equipment function -- gas turbines don't spin well when iced solid).

Pumped-hydro is the most efficient storage solution bar none, but is painfully restricted by siting opportunities. Being able to use oceans as a lower baisin might address this, though salt-water engineering is a significant concern (corrosion and other issues).

Interesting to see molten salt as at large scale that pencils out a viable for even, say, a two week total energy replacement solution for the US. You'd need tankage (insulated) roughly corresponding to current Oaklahoma oil transshipment storage facilities.

Electricity-to-fuel is another option, with Sabatier and Fischer-Tropsch cycles both proven. Carbon source from seawater appears somewhat promising, though my concern is that there's been 50 years of research without a large-scale demonstration project, making me suspect deeper issues.

I actually am a fan of load-shedding, and suspect that the concept of dispatchable load as opposed to supply may be part of the future way of thinking.

Coal => gas is a no-brainer, though also not a total solution, by a long shot.

Geothermal is highly underrated, especially if currently protected areas are opened for consideration. The Yellowstone caldera could possibly supply up to 15% of total US electrical demand.