well there is a difference between empires collapsing and civilizations collapsing.
When the Western Roman empire fell, its civilization continued and continues today.
When the Roman empire as a whole fell (1453), it did collapse - replaced by Islamic civilization. Of course we could argue that 1453 was just the culmination of the long decline from about 1240.
British “civilization” didn’t collapse - it continues even in the legal code of India etc. - it morphed.
The Mayan civilization collapsed as did the Hittite, the Assyrian, the Khitan etc.
“When the Western Roman empire fell, its civilization continued and continues today.”
I disagree. After the collapse of Rome it's civil society disintegrated. All of Europe that wasn't part of the Byzantine Empire descended into the hundreds years long Dark ages. All of the rest was eventually taken over by the Muslims.Fragments of Rome was past on via the Catholic Church primarily the Latin language. Rome's traditions and social structures were replaced by Europeans tribalism which evolved into monarchies which themselves have gone by the wayside as a governing force.