Yes power out for a few weeks
It’d be Omega Man
Our electrical grid includes a number of custom designed LPTs, Large Power Transformers:
“Key industry sources have identified the limited availability of spare LPTs as a potential issue for critical infrastructure resilience in the United States”
These are very expensive and have a long lead time. And naturally, thanks to bipartisan support for globalism and American de-industialization, we no longer build them. We probably no longer know how to build them, having surrendered the institutional memory along with the plants capable of making them.
Anyway a truly serious and angry opponent would knock these units out and let us wallow in the resulting chaos. It would take a very long time to recover. No nukes needed.
A smart country would encourage decentralized power generation in order to reduce this system risk.