Why some companies are reporting loss due to the new US tax law? From http://uk.businessinsider.com/bank-of-america-fourth-quarter-earnings-q4-2018-1?r=US&amp;IR=T:


  Like the other big banks, Bank of America took a hit from the recently
  enacted tax law, writing down \$2.9 billion primarily in deferred tax
  assets that declined in value.
  
  JPMorgan earlier reported a \$2.4 billion fourth-quarter loss because
  of the new tax law, and Citigroup reported a $22 billion loss.


My simple minded expectation is that when you lower a tax rate companies should have more money.

I tried reading about 'deferred tax assets':
https://www.investopedia.com/terms/d/deferredtaxasset.asp

Where I found:


  The simplest example of a deferred tax asset is the carry-over of
  losses. If a business incurs a loss in a financial year, it usually is
  entitled to use that loss in order to lower its taxable income in
  following years. In that sense, the loss is an asset.


So perhaps there is a place for clever accounting around expenses and taxes. But what is the exact mechanism? Why some companies are reporting loss due to the new US tax law?
The lower tax rate means that they will gain less benefit when they apply their deferred tax assets against their income. 

They have large amounts of these assets recorded on their balance sheets and are adjusting them to reflect the new, lesser value.