Kraken and Poloniex are registered in USA. Even they will ditch the US customers, it means nothing because they are doing business from USA without being MSB.
Yep. And regardless of what they do now (like registering and moving operations to another jurisdiction), it can't erase the past several years of operation in the US, and serving US customers. It sucks to be a US resident right now if you haven't been paying your taxes (can't send those coins to regulated exchanges). Also sucks to be Kraken, Bitfinex, Poloniex, Bittrex..... but especially the former two, because they've been processing fiat withdrawals as well for years.
Polinex and Bittrex don't do fiat.
Bitfinex is tightening requirements for US customers, maybe first signs of a pull out from the US.