Any seismic regulation would've probably completely blasted a building where roof is not held in place in tension. In general, remains seem to lack any continuous reinforcement in between panels. Only flimsy fasteners held them together.
USA is a land of contradictions, and its building codes are no exception.
They write 100 pages sections of building codes regarding fire resistance, down to mandating which kinds of doorknobs can be installed, and then allow people building stuff from plywood.
Same for building in hurricane/tornado areas. It's absolutely nobrainer how to build buildings capable of withstanding any imaginable hurricane.
But instead of just banning anything not built from reinforced concrete, or steel, they keep trying to "rationalise" building methods which would still have zero chances surviving a tornado, even if laden with every reinforcement imaginable.
Most buildings are in this category, and it make sense. This is not where the fault lies.
Building something to specifically withstand 200mph wind is NOT reasonable. Hurricanes force wind by comparison starts at 74mph and decays quickly inland.
A properly engineered reinforced concrete building would easily withstand that.
Could that be changing as the climate changes?
Like seeing 500-year floods several times in 20 years.
You could build a building like a tank, but it would price most people out of the market. Doors and windows in that structure won't be able to withstand the obscene wind forces however, so everyone inside will still likely be killed by the airborne debris, anyhow. You really wouldn't have time to install steel shutters on the windows and bar all the doors like you'd need to. But hey, the building will remain standing, so that's a win, right?
Instead of all of that, just requiring a small emergency shelter in each home might actually keep the occupants alive.
https://www.computerworld.com/article/2497174/tornadoes-and-...
In particular, the hundred-ish year old design called a Quonset Hut is partly designed for this wind-deflecting purpose.
At that square footage, the semi-circle arc (which is its main wind-deflecting feature) would have to be gigantically tall. It doesn't sound like a feasible geometry at that scale.
[1] http://varnumcontinentals.org/2016/04/the-quonset-hut-a-rhod...