Is an 11 trillion dollar debt and polarized political parties symptomatic of a failing democracy?

I am afraid that it is. The quote that you cited from Alexander Tyler was, as you are probably aware, an incremental explanation of how a republic disintegrates and becomes a dictatorship. I have no idea how the trend can be derailed without blood flowing in the streets. At sixty-eight years perhaps I will not live long enough to witness the outcome. I have mixed emotions regarding that possibility.