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.
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.
. So Binance stay one step of the game by offering a separate trading for US residents only. It's a bold move, but at least they have dodge another bullet in doing that.