Although BitFinEx has previously indicated that it will no longer allow American people to access the services of these exchanges. They are unable to access the Exchange's margin trading services. This has been posted on Reddit after searching by many related American corporate clients of BitFinEx. This BitFinEx support portal currently says that restrictions do not affect US corporate clients.
Bitfinex Restricts U.S. Corporate Account Holders From Accessing Margin Markets
Margin Traders Left Unable to Close Positions
Source - https://news.bitcoin.com/u-s-corporate-customers-barred-bitfinexs-margin-markets/