But they are not going to leave anyone behind, they are going to establish a separate trading platform that would work accordance to all US laws for providing service to all US residents. The platform would probably be called Binance US.
Changpeng Zhao said it's going to be a fiat-crypto exchange. It'll probably be more like Binance.je than Binance.com, but hopefully I'm wrong and there will still be lots of available markets for US traders.
I believe part of this has to do with offering security tokens not registered with the SEC, and Binance's unwillingness to register as a national securities exchange. Bittrex and Poloniex have made similar moves. It's possible that most markets will still be available on the .US domain, minus a few dozen of the obvious securities.