> Building bunker capacity for every citizen is definitely about size. The US is incredibly spread out compared to most European countries.

Not really, it's per capita, not per area. There's nothing physical about America that would prevent it from requiring developers to add a shelter to every housing unit or in every housing development, like Switzerland does. Likewise, there's nothing physical preventing America from building and maintaining public shelters in denser urban areas.

The article also mentioned Sweden has public bunker capacity in urban but not rural areas. There's not physical reason American could not do something like that.

It depends on whether you want to build bunker capacity for every citizen or just the half that live in cities. It's just cities, you have to convince all the suburban and rural citizens to pay for it.

You could imagine this being accomplished at a city-wide level out of city budgets and local taxes, but again this just reinforces the point that size is a problem.

Sweden's population is more concentrated in cities than the US's population. In the US, rural voters have a dramatically outsized influence over the senate.