On August 10 a Filbert tree branch contacted a power line and shorted it out in Eugene Oregon. That was part of a chain reaction that took out 8 states including Colorado.
The way it was explained to me One "generation unit" went out and that put an overload on the next generation unit and it went down and before it was all over 8 generation units went offline and the whole grid went down.
When I worked for HSS/G4S we had a guard detailed to drive from Colorado Springs to the New Mexico border every week and check the transmission lines.
There's a power plant in Colorado Springs that's owned by a power company in Texas all the power it generates goes to Texas.
Texas buys power from Colorado. Colorado buys power from Kansas. Kansas might buy their power from New York (hypothetically). So a power outage in Colorado could affect the whole country.
I was talking about this to a utilities employee one day. Apparently he worked for the Utilities provider