Thinking about this yesterday except along the line of British colonies. Each colony they lost is a marker in their decline. One may say it is the beginning of the weakness that has culminated in the surrender of their sovereignty to the barbarians.
This is analogous to us and Europe. Europe has effectively been our colony since 1946 with the apex marker being the retreat of the Mongols and the fall of the Berlin wall. Since the retreat of the Mongols from the US at Berlin, we have had inept, poor (43 failed to complete the missile defense in Poland), and misguided administration Today, Europe is rudderless and the Mongols are looking at it with a lusty, hungry look.
Loss of these colonies will be a demonstrable marker of our decline.