No nation is so big and so powerful that it does not fall prey to the iron laws of the survival of its civilization. A civilization will continue intact as long as the people, or race, who built that civilization, remain present.
As soon as those originating people disappear, or are assimilated into a new racial group, then that original civilization will "fall" or become changed to reflect the new racial population make-up.
This is why the Ancient Indo-European civilizations in the Middle East lie in ruins;
Above: The ruins of the palace of Darius, King of Persia
This is the reason why the Ancient Egyptian civilization lies in ruins;
Above: the ruins of the temple of Ramses II, Thebes, Egypt
This is the reason why the Ancient Greek civilization lies in ruins;
Above: the ruins of the Parthenon, Athens.
This is the reason why the Ancient Roman civilization lies in ruins:
Above: the ruins of the Forum in Rome.
In each and every one of these cases, the original White population was displaced by an immigrant non-White or mixed-race population. The very nature of those civilizations was changed as the new, largely mixed-race population, was unable to maintain the original technical and cultural levels of the White civilization. These civilizations "fell" because the people who created them, vanished.
And now, as the United States of America starts to change its racial make-up, the same factors are at work: formerly White cities are turning into ruins, quite literally. To view the modern US equivalents of the ruins of White civilization, follow the individual city links listed below.