When the global economy starts to turn around, the U.S. will have to pay the piper for its structural debt. Creditors won't buy up U.S. securities forever, and when they start looking elsewhere for better returns, the U.S. will start monetizing its debt. Or else do you think voters will say, "So you want to default on Social Security and Medicare while raising taxes across the board by 10%? Sounds great!" And if the U.S. can't find buyers for its securities, how is it going to control the money supply?
Once the U.S. starts monetizing its debt, hyperinflation will take hold.
Long-term, I do not expect the United States to turn into Zimbabwe, but I definitely see something like an L-shaped downturn where the economy shrinks 15% and remains stagnant thereafter.