That'll take down any society.
I have a friend who is a scholar on Rome. I asked him.
“Rome was great so long as her Legions were great.”
Hundreds of books with thousands of words offer all manner of reasons but none quite as concise as these words.
Teddy Roosevelt on the Fall of the Republic
"The Roman Republic fell, not because of the ambition of Caesar or Augustus, but because it had already long ceased to be in any real sense a republic at all.
When the sturdy Roman plebeian, who lived by his own labor, who voted without reward according to his own convictions, and who with his fellows formed in war the terrible Roman legion, had been changed into an idle creature who craved nothing in life save the gratification of a thirst for vapid excitement, who was fed by the state, and who directly or indirectly sold his vote to the highest bidder, then the end of the Republic was at hand, and nothing could save it.
The laws were the same as they had been, but the people behind the laws had changed, and so the laws counted for nothing.”
Rome's decline begin when the people abandoned their Republic in a favor of a Democracy. They exchanged the rule of law for the rule of the majority.
Can you honestly say that is not happening to Americans' constitutional guarantee of a republican form of government?
Oh, wait, you're not asking about the actual fall of the Roman Empire in 1453? You're asking about the non-event in 476 when the last Western Augustus retired to a villa near Naples, that Gibbon and the other "Enlightenment" historians trumped up as "the Fall of Rome" so they could dispossess the Christian Roman Empire with its capital moved to "New Rome" as Constantine the Great called it, Constantinople to everyone else, of its Romanity by inventing the fiction that it was a different "Byzantine" Empire, rather than the Roman Empire.
It's really hard for me to put much stock in trying to analyze deep social or political causes for the decision of the Eastern Augustus to stop having a Western counterpart and rule as sole Emperor.
Read a good history of the whole Roman Empire written by a competent "Byzantinist" who ignores Gibbons' propaganda, then circle back around and read Henri Pirenne's Mohammed and Charlemagne, to fill in the history of the West from 476 through to when the West stopped even theoretically being in the Roman Empire because it set up its own parallel version under Charlemagne (which as Voltaire waggishly noted was neither Holy, nor Roman, or -- after Charlemagne's death -- and Empire).
I did a study on this several years ago.
I was surprised at the similarities.
It is hard to read Edward Gibbon’s “The Decline and Fall of the Roman Empire” without being frankly frightened by the parallels.
Agendus XXI
As for parallels between empires Roman and American, I suggest you take a look at this book from 2005 (or the updated version, after the housing bubble popped--it's expanded, not revised). Even though their book is about financial stuff that most of us here already know--hopefully--in the course of the narrative, the authors draw a rather gloomy word picture of America's descent into empire in the Roman tradition, commencing exactly 100 years ago, rehashing in detail various socio-economic conditions that led to the Roman Empire's collapse, suitably buttressing their (at the time, minority) opinion that the United States is, indeed, an "empire of debt."
Does 1913 ring a bell in your mind? A triple-whammy, right?
Special interest groups fighting and working against each other instead of for the common good.....
Christianity - Life and the future seemed hopeless for the millions who were ruled by Rome where an early death was almost inevitable. Christianity taught the belief in an afterlife which gave hope and courage to the desperate. Eventually a Roman Emperor, Constantine the Great, proclaimed himself a Christian and issued an edict promising the Christians his favor and protection. Attitudes in the Roman Empire changed from being antagonistic to becoming pacifistic"
Not sure I quite follow this (sarcasm - it's actually complete crap logic - no logic attempted.) This seems a typical shot at Christianity inserted by the publisher and not in the original text. It's not even a very good attempt. If a loss of Morals and Ethics were destroying Rome ... how exactly did Christianity help destroy Rome? Again - even without all the obvious counter-arguments, they don't even make a case for it, except to weakly suggest that 'antagonism giving way to pacifism killed Rome' ... but Christianity is not exactly pacifistic ... Jesus came with the sword.
One needs to consider that as the massive bureaucracy crumbled, warlords rose to power and the Christian Church rose as an institution. My take is that the authority of Rome fell to local power.
They instituted the Dole and started giving some folks free livings so they could make music and paint pretty pictures...
If you were a poor Roman you got grain from the state and could live on that.
If you were a rich Roman you could retreat to your estate and meet your needs with what your slaves produced.
So defense and other public responsibilities were left in the hands of foreigners who weren't always loyal to the empire.