No electricity in Russia = people making do as best they can in an orderly, civilized manner.
No electricity in America = riots, looting and anarchy.
There's no need for missiles, bombs and military mobilization to bring America to its knees. It can be done by someone sitting at a computer terminal. The enemy is us. The Russians know this.
Instead Russia is busy organizing the majority of the worlds economy against us... and Biden helped by seizing Russian assets in our banks.
No need to nuke idiots destroying themselves.