True that US customers are banned from Bitfinex, however they did recently announce that bank deposits and withdrawals are reopened for other countries. If you don't believe them that's fine, I don't trust them either, but they did announce it. https://www.reddit.com/r/BitcoinMarkets/comments/7enpoo/bitf...
The first string of comments says they haven't announced yet (besides on reddit) and nothing on their site claims anything to that affect either.
Also, if the Fed barred any Bitcoin sales/buys with USD (however unlikely) almost all reputable bank would drop those as well, regardless of country. This has been discussed in detail on r/BitcoinMarkets, actually.
