Also the zeroth failure mode: someone built a bridge that will collapse if any of the many many large ships that sail beneath it can't steer itself with high precision.
They weren't freight ships destined for Baltimore, but it wasn't hard to imagine future freight ship sizes when designing the bridge in the early 1970s.
The London sewer system was designed in the 1850s, when the population was around two million people.
It was so overdesigned that it held up to the 1950s, when the population was over 8 million. It didn't start to become a big problem until the 1990s.
Why the bridge piers weren't set into artificial islands, I can't fathom. Sure. Let's build a bridge across a busy port but not make it ship-proof. The bridge was built in the 1970s, had they forgotten how to make artificial islands?
The organizations that made the bridge happen were so much more vast and so much higher turnover and subject to way, way, way looser application of consequences than the one that built the fort it would be literally impossible to get them to produce something so unnecessarily robust for the average use case.
This sort of "everything I depend on will just have to not suck because my shit will keel right over if it sucks in the slightest" type engineering is all over the modern world and does work well in a lot of places when you consider lifetime cost. But when it fails bridges fall over and cloudflare (disclaimer, didn't actually read that PM, have no idea what happened) goes down or whatever.
Unless the military was relocated to Mars (or at least the Moon) during the shutdown, I think the word is "metaphorically" instead of "literal".