Every one of these potential attacks would require a lot of things to go very right. It's easy to do X or Y under experimental conditions. The real world is far more chaotic and the odds of success are lower.

Further, none of these things would cause an enemy to capitulate. If an enemy shut off power or caused car crashes in several major cities at once, the US isn't going to just surrender or even think about it. They're going to strike back with the widest array of options for employing force that earth has ever seen. Every option you listed would be pin pricking a giant.

Cyber warfare is super cheap, but it's also orders of magnitude less effective than sustained aerial bombardment or a complete naval blockade. Another tool in the tool chest, but not something I would base my national defense on