It’s not rot. It’s not decay.
It’s corrosion!
The difference being, there is an active agent involved in the decomposition of the substance that was America.
Corrosion penetrates and dissolves.
You can see this in nearly EVERY aspect of society, culture, economics, and government.
It is simply impossible to believe that this is a random degeneration of quality of our essence. This is deliberate.
No, it's rot.
America has always been subjected to outside evil forces (your words: active agents) which have attempted to attack our core values, undermine our fundamental principles, etc.
The difference being: We are now inviting our attackers in / welcoming them with open arms / smugly viewing ourselves as "morally superior" and "virtuous" when we agree with our detractors..
Regards,