POTUS is threatening to shut down the government if Congress doesn’t fund his stupid Southern border wall. It’s not going to happen. The shut-down may happen or Drumpf may back down as he often does. But it’s not the big economic threat.
The big economic threat, as many here have pointed out, is the danger of breaking the artificial (and probably unconstitutional) “debt ceiling,” that prevents the govt. from further borrowing to pay its bills, bills that it has already incurred. Since the economy of the entire world is tied to the stability of the U.S. credit—namely, that we always pay our bills, we never default on our debts, this is a huge threat. Our never defaulting is not an accident. It’s even in our Constitution, “the full faith and credit of the United States shall not be questioned.” The Democrats are going to want a “clean bill,” that is a raising of the debt ceiling without any "poison pill" amendments. The Freedom Caucus of the Congressional GOP will, by contrast, want some nasty bribery (e.g., funding for the Southern border wall, or defunding of Planned Parenthood, or repeal of the ACA) to vote for the raising of the debt ceiling. They could well break the debt ceiling since they are delusional and think the consequences will be minor (whereas it will probably lead to a global recession).
I now believe that the likelihood of breaking the debt ceiling is greater than 90%! I don’t think Paul Ryan, even with Democratic help, has the votes to get the debt ceiling raised. And without poison pill amendments, I think Drumpf would be stupid enough to veto a clean debt ceiling repeal.
I think we had better brace ourselves for a debt ceiling break and consequences: global stocks tanking, massive unemployment, and numerous countries calling in our debts. Now, the GOP will pay a price: Loss of one, maybe both chambers of Congress in ‘18, and a huge Dem wave in 2020. But it will take DECADES for the USA to restore its credit—if it ever does. It will be bad, folks. And I think we need to brace for it.