American Banks and accounting rules

 Apologists for America’s largest banks say that they are smaller than their European and Asian competitors … and that they have to be big to compete.
Current Vice Chair and director of the Federal Deposit Insurance Corporation – and former 20-year President of the Federal Reserve Bank of Kansas City – Thomas Hoenig destroyed that argument earlier this month.  Specifically, Bloomberg reports:

Warning: Banks in the U.S. are bigger than they appear.
That label, like a similar one on automobile side-view mirrors, might be required of the four largest U.S. lenders if Thomas Hoenig, vice chairman of the Federal Deposit Insurance Corp., has his way. Applying stricter accounting standards for derivatives and off-balance-sheet assets would make the banks twice as big as they say they are — or about the size of the U.S. economy — according to data compiled by Bloomberg.  “Derivatives, like loans, carry risk,” Hoenig said in an interview. “To recognize those bets on the balance sheet would give a better picture of the risk exposures that are there.”
U.S. accounting rules allow banks to record a smaller portion of their derivatives than European peers and keep most mortgage-linked bonds off their books.

Enron was "legal" for the most part.  Mark to market was an accepted accounting technique and so is the one described above.

American Banks ARE NOT Smaller than their Foreign Rivals | The Big Picture