It is giving the world an object lesson on how a small but ruthless and suspiciously well-financed, minority of ideological extremists can hijack an entire nation and undermine the fundamental principle of democracy - the majority rules. Even in America.
Shutdown: inability of two parties to negotiate a compromise. One party is stuck with a "negotiation" position that the other can't live with, and can't find a reasonable alternative that is acceptable to both sides. Debt Ceiling negotiations: this is the biggest worry. Shutdowns happen fairly frequently (56 times in recent years) and about half the time one side extracts budgetary or legislative concessions. Actually, because they force people to make difficult budgetary decisions, they are useful. But this is only because the consequences of a default are so dire, for the US and the rest of the world. The date for the debt ceiling? Oct 17.