• The “mother of all bubbles” is due to pop soon as U.S. outperformance has been inflated by massive amounts of debt, warned Ruchir Sharma, chair of Rockefeller International.

The U.S. has become too addicted to debt, and attempts to rein it in will eventually weaken economic growth and corporate profits, according to Ruchir Sharma, chair of Rockefeller International.

The market expert followed up his earlier “mother of all bubbles” warning with another column in the Financial Times last week that laid out how the bubble of U.S. outperformance versus the rest of the world will pop.

While Wall Street bulls point to strong earnings, Sharma said the record is less impressive after adjusting for government spending and the handful of tech giants with massive valuations, adding that “supernormal profits” tend to return to normal amid competition.

“Growth and profits are also getting an artificial lift from the heaviest deficit spending ever recorded at this stage of an economic cycle, by far,” Sharma, who authored the recent book What Went Wrong With Capitalism, explained.

Indeed, debt held by the public, or the amount the U.S. owes to outside lenders after borrowing on financial markets, is already at about 100% of GDP, with that ratio soon expected to blow past the all-time record set in the immediate aftermath of World War II. But this time, it will take place without a global catastrophe while the economy remains robust.

The cost of servicing all that debt has also exploded and is contributing to deficits as well, creating a feedback loop on the debt. Interest expenses for the debt are now $1 trillion a year and are among the biggest budget items, even exceeding defense spending.

Still, while the federal government is awash in red ink, U.S. households and companies maintain strong balance sheets that can continue fueling the economy. In fact, third-quarter GDP growth was revised up to 3.1% from an earlier reading of 2.8%, due in part to more consumer spending.

“But every hero has a fatal flaw,” Sharma wrote. “America’s is its sharply increasing addiction to government debt.”

According to his calculations, $2 of new government debt is required to generate an additional $1 of GDP growth, up 50% from five years ago. Any other country with similar dynamics would be suffering from capital flight by now, but the U.S. can still boast the world’s top economy and reserve currency, he said.

One catalyst that could bring an end to the party is if markets get fed up. Sharma predicted that next year investors will likely demand higher interest rates on all the fresh debt being issued or some sign of fiscal discipline. That will lead to efforts to reduce dependence on government spending, which will hurt growth and profits.

There are already signs of that happening as bond giant Pimco said it is reducing its exposure to long-term U.S. bonds amid concern about soaring debt.

Or, other top economies, like in Europe or China, could rebound and erode America’s relative outperformance, he added. There could also be totally unforeseen events.

“In the late stages of a bubble, prices typically go parabolic, and over the past six months US stock prices have outgained others by the widest margin for any comparable period in at least a quarter century,” Sharma said. “When flying in such thin air, it doesn’t take much to stall the engines. All the classic signs of extreme prices, valuations and sentiment suggest the end is near. It’s time to bet against ‘American exceptionalism.'”