Most are relatively small in number of active population revolting, while when hunger bite all have very little to loose so while perhaps not united they all unrest.
As you rightly say society is complex, so we can't just simplify to us vs the enemy, not matter what, but humans needs are not that complex and human psychology is still essentially the same in millennia. The ancient "panem et circense" is still valid, just to cite one famous governing model still used today. The social ignorance and complexity is used by those who rule to grab and stay in power, but again with not really different principles than 1000 years ago, just means/tech/scale is changed.
Any dictatorship to remain in power need to satisfy enough his subjects and/or find enough justifications for those who aren't satisfied, that's why most dictatorship grow fast, giving back an apparent good/fast evolution then when resources start to be scarce they push toward war/blame opponent etc and again that's might last or not but in the end they fall. A new society rise on the ruins of the precedent. We are probably around one of those changes were wars can't work anymore alone. At those points populations rise, no matter how much united, they rise ad a big destructive force no one can resist.