It's actually ridiculously easy to take out power for large areas with a rifle - https://www.stgeorgeutah.com/news/archive/2016/09/26/jla-tho...
As for attacking the wind turbines, I would be much more worried about a malicious actor turning off the brakes during high winds - https://www.youtube.com/watch?v=ucceQ3vS3zs
People are quite reasonably more afraid of attack vectors that can affect huge numbers of people all at once, especially when the attacker could be anywhere in the world.
One obvious example of why that's reasonable is the recent ransomware – sure, you've always been able to easily extort $300 from someone, but now you can take money from a lot of people, and not get caught.
Hacking is something that is getting more and more likely by the day. First, WannaCry infects the world over and knocks out a hospital system. What's next? Pacemakers going offline? Insulin pumps being hacked? Hell, cars can already be hacked from a distance, internet connected cars aren't raising a risk factor by much, aside from it lengthening the distance at which you can do the hack.
Now imagine that on every bridge. It only takes one car to bottle up a lane.
All it takes is a length of chain or some graphite powder.
SOP for fire departments responding to branches on lines that haven't brought the lines down is to call the utility then babysit the tree branch until it finishes burning.
The current passed by a tree branch depends both on the resistance of the branch and the voltage of the line. In the video I linked it was clearly enough of a short to ionize the air and cause an arc that would damage equipment quickly.
And I don't know who the author got this idea from: "The equipment is designed for lightness and efficiency, and is often fragile as a result.", but it's not accurate. It's designed for a balance of performance, robustness, and cost. Just because the machines are not designed for repeated emergency braking or doesn't make them fragile.
Bigger picture though, next time you're out and about take a good look at your surroundings. The U.S. is huge, and much of our grid infrastructure is remote. Forget the nuclear power plant example in the article. It wouldn't be stupendously difficult to take down a major transmission line or switchyard if you were determined. Much of the world operates because people generally leave well enough alone, for better or worse.