It won't this time. The inter-dependencies of today's technology is much deeper and the knowledge base to keep it going is highly distributed. The knowledge itself is way more complex than that of the Roman era.
Ethno states will do just fine.
—China
—Japan
—India
—Israel
—Saudi Arabia
—Russia
It is the “melting pots” of the West that are facing dissolution and doom.
and can be stored and transmitted anywhere. It's backed up in multiple locations.
We're reverting to where we'll have people "discovering" computer equipment in garbage dumps the way people find ancient coins in European gardens.
Like when painted natives on remote islands would see airplanes flying overhead, people living among ruins of cities connected by abandoned rail lines and unused roads will see satellites passing overhead at night, steadily blinking as a reminder that people in other parts of the world moved on.
They'll be kept intentionally ignorant through indoctrination, given government scripts to believe and plenty of soma to keep them from thinking.
It started a century ago.