Unfortunately, this is a little too simplistic.
A democracy doesn't exist in a vacuum; there are competing nations that are at work to undo or subjugate yours, and this never stops. We've lived a charmed life these past 80 years that are unlike any in the history of the planet.
American wealth and power are what brought this unprecedented stability to the western world, but it has been eroding.
As it erodes, the flaws in the American system begin to show, and then fray. The very means by which Americans elect automatically pushes it into a two party system, which is by nature polarizing, especially when external pressures come to bear.
It's also incredibly difficult to change course safely when so many people are involved (this affects all organizations, which is why startups can eat their lunch). Assuming that you can dynamically rise to the challenge is naive at best.
Federation only amplifies the problem, as you simply add more uneven competitors to the national riches.
I could cite dozens of times a society has gone 80 years (4-5 generations) without serious threat from foreign parties. How is our case unlike those?
The entire world has seen greater technical advances in the past 80 years than any time before, but zero percent of that is related to the politics of any one nation: either causally or effectually.
I don't know, it doesn't seem simplistic in conclusion. The article describes a dynamic environment and you're just postulating further variation than described there. That doesn't mean the ideas don't agree or that the general formula isn't sufficiently complex to incorporate more nuance than the article lays out.
The linked solution isn't as interesting, mainly because the idea of there being a solution seems the simplistic part. It is a system and it will play out.