I suspect there are two realistic ways to "attack" an infrastructure. The first is to destroy it. Blow up airports, damage planes, that sort of thing. Blow up all bridges, or miles of railroad tracks.

The second would be to deny use. I don't have to steal your car if my motive is to deprive you of transportation. I could just disable it.

I think any group hostile to the US could hamper our use of roads and rails simply by attacking ONE target with a military weapon not available to the average bear(hunter).

The ensuing protection and regulations would easily hamper the entire industry. I would bet they could cut 10% off the efficiency, an enormous cost. And wouldn't have to destroy 10% of the infrastructure to do it. That would be expensive even to destroy, people could be caught, and so on.

Easier to just make the use of some segment too unwieldy to really use.

And, Americans don't get too upset over the loss of life to violence. Isn't it around 50,000 per year dying in car wrecks.

We'll gladly pay the price on occasion to avoid inconvenience.

Arf (I don't know - how many bullet dents were found on a telescope mirror crating? Maybe none - bullets cause dents, don't get dented?)