Russia, China, and most of the rest of the world has interconnected their grid with other countries.

This is a map of where the grid is frequency matched across internal borders allowing easy exchange. DC connections don’t need this synchronization, but it reduces losses with AC. https://en.wikipedia.org/wiki/Continental_Europe_Synchronous...

In war this might be a minor issue, but in war electrical infrastructure ends up a target so it doesn’t matter that much.