Tax receipts drop sharply and big government deficits return. The exploding trade deficit sinks the dollar. Foreign investors pull dollars out of the U.S. Capital flight leads to devaluation. Illiquidity and credit risk cause interest rates to soar. Counterparty failures set off a chain reaction of derivative losses.
Insolvent debtors collapse the bond market.
The U.S. government can no longer fund all of its programs or meet every financial guarantee. We will be lucky if we get off with no more than a depression. If too many jobs evaporate and the government's payments don't get out on time we have the possibility of state socialism. A desperate government will do desperate things. Frantic politicians and worried voters could conceivably push for currency controls, confiscatory taxation, nationalization of industries, massive unionization, gold confiscation, wage and price controls, subsidies, debt monetization, rent controls, and heavy inflating.