The risk of very high altitude "super EMP" nuclear attacks is the most concerning. If Taiwan were attacked, it would stand to reason that China would first create CONUS disasters against infrastructure without a direct, kinetic military attack. This would be most effectively deployed by EMP at very high altitude while simultaneously sabotaging infrastructure with hacking.

https://en.wikipedia.org/wiki/Microgrid

If solar on rooftops (with batteries or EV connections) became really widespread in the US it may make some sense to be able to isolate communities from the rest of the grid to localize failures. Utilities would probably hate it but it could be really resistant to disruption.

I mean, I don't really understand why they'd hate it. I'd hope they'd embrace it. Deploying batteries for communities would allow utilities to still support things like net metering while also also allowing them to turn off grid connection for an area so the main lines can be worked on (without disrupting service).

It'd also give them a lot more time to address outages, even really severe ones.

Not to mention their ability to better control load and generation with rapid response batteries.

If someone attacked all the interconnects then the net importers would lose power or brown out while the net exporters would be just fine. (assuming the net importers are currently running power generation at capacity).

For the grids under load, if more capacity can't be brought online they'd do rolling blackouts while working to restore the interconnects.

There are far better targets for a coordinated terrorist attack if they wanted a larger impact.