When not caused by war, nations decay slowly and gradually (e.g., modern day France, Italy, Spain, Greece etc.).
Alas, now, it seems ours is no different. Its exceptionalism is dissolving into the ordinary. It’s a choice made by the people. They fore-go liberty and self subjugate themselves under ruling political and administrative classes of which they’ll never be a part. They’ll never rise to those classes because they’re taught apathy, complacency, and their place since birth. They are relieved of the burdensome onus of everyday decisions. Decisions that were proudly made by preceding generations that were not a bother or an onus at all to them. To them, it was life. Deciding what to do, how to live, and how to be was essential and culminated in traditions, virtues, and mores.
That became too onerous for the generations that followed, they blithely go about taking direction and surrendering thinking and creativity to others in the elite political classes.