Seems like that they are scared by the fact that BTC-e basically got brutally taken down by the US government, and they want to vaoid the US government as much as they can because they know that even with their KYC standards it might not be enough.
And plus as they said the effort and money put into handling US side of things is just too large.
Most of Bitfinex's users aren't even US citizens, meaning that discontinuing US users will lessen their profit, just not by a very large margin at all.
Just use some other exchange if you're in US and still want to trade. Most of them are still open for US, but some ban specific states.
Bitfinex lost it's ability to move dollars in April this year. And zero hedge wrote the following article about them in May:
http://www.zerohedge.com/news/2017-05-03/worlds-largest-bitcoin-exchange-headed-mt-gox-style-collapseCould Bitfinex, the world's largest, Hong-Kong based cryptocurrency exchange, be headed for a Mt. Gox-style collapse? It's starting to look that way.
When Mt. Gox first halted customer withdrawals in February 2014, it waited more than two weeks to admit the truth to its customers: that hackers had stolen more than $450 million of their assets, leaving the exchange bankrupt and them holding the bag. That hack effectively crippled the entire digital currency ecosystem, ushering in a two-year bear market that at one point carried the bitcoin price below $200, from what was then a record high north of $1,200 reached in November 2013.
So when another exchange engages in similarly shady behavior - withholding critical information about customer funds, or failing to produce audited financials despite promising to do so - it should prompt crypto traders to ask themselves why, with dozens, if not hundreds, of cryptocurrency exchanges operating around the world, they're choosing to do business with this one.
The writing has been on the wall for some time.
If people have coins there, start moving them now. Don't wait 90 days.