Public infrastructure needs quite a lot of work to make it work and care about it. You need a constant stream of engineers, technicians, materials, money, etc.

Public infrastructure needs quite a lot of work to make it work and care about it. You need a constant stream of engineers, technicians, materials, money, etc. And quite a lot of coordination. So even a first world country can fuck it all up and you wouldn't need a spectacular failure, just a bit of time, and a bit of willingness/resources shortage too. You can build a more, say, resilient infrastructure, but I don't think anyone builds infrastructure like The Romans did today.