It’s sort of a weird trope because the level of justification is wildly uneven.
As a method of taking down power grids it’s alarmingly effective. Even quite prosaic rifle fire(ie. not some sort of exotic anti-material gear; just friendly ‘modern sporting rifles’ as they’ve been rebranded) will at least penetrate the housing of a transformer and cause coolant leakage and at least risk of damage to the windings(either direct or from arcs and shorts); and transformers are relatively widely distributed, ill-monitored; and the bigger ones have substantial lead times to replace.
There’s already a modest but concerning backlog of cases where parties unknown picked a substation, shot it up, and left without being noticed or subsequently identified; with times to restore service stretching into multiple days and requiring specialty items(like truck-mounted portable transformers) that are themselves not in generous supply.
As a method of kicking off the racial holy war and/or self-destruction of decadent society the record is…markedly less impressive. People have been losing power to various flavors of inclement weather and enduring both lack of power and the aforementioned weather largely without incident for decades; more or less going back to electrification. Significant economic and logistical disruption; often a few deaths among those dependent on electrified medical services or most thermally vulnerable; but that’s about it.
Had someone actually managed to hit 5 substations in the Baltimore area in quick succession there would likely be some very, very, unhappy supply chain conversations going on, possibly all the way back to grain-oriented electrical steel; but the theory that Baltimore would obviously tear itself apart because obviously only a continuous supply of Aryan Current can keep a 57% black population from turning into a zombie movie with more drug gangs is the lunatic part.
