In Cyprus, we had such an event in 2011, when 2000 tons of explosives Russian tried to smuggle into Syria, were intercepted by a U.S. Navy and redirected to be offloaded here (because the ship carrying them was formally registered here and flew a Cyprus flag - really being owned by the KGB), and these explosives went off in the summer heat, wrecking a power station that produced 70% of the electricity here.
We only had about 2 hours of blackout per day and a recommendation to limit a/c use, for about a month.
Power transmission is super resilient and relay protection is a whole science of it's own. Especially in the U.S. when there are many virtually independent, privately owned and loosely interconnected transmission systems, which puts it at a relative advantage.