Now presuming that this particular attack was not caused by terrorism it does point out a possible future target to terrorist cells that would be low risk and easily done. Causing an arc between two high voltage transmission lines would take out those lines. Bringing down a couple of towers which support high voltage trans mission lines would also bring down that line. I can come up with a cheap means to take out an electrical substation using only legaly available substances that are effectively untraceable and legally it would not even qualify as a destructive device. Such a device could be employed by one person acting alone.
I can come up with a means of taking out an electrical transmission line that uses bronze age implements and one person. How many such lines have to be taken down to cause wide spread power failures bring down the grid? I did not go into details because I do not want this to be a how to instruction but five people could take down the grid at least as seriously as this outage and possibly covering a wider area and meaning it would take significantly longer to be back on line.
Now we are also talking some real economic damage here beyond the initial inconvenience. If combined with another attack then we are talking some serious damage to the USA.