There are many reasons why a bank might close an account. Assuming that a huge deposit from the undisclosed sales of Sumcoin by BMCS is one of the least likely reasons. So far, Miller has not given a legitimate reason for it. Why?
A material event such as the successful completion of the Sumcoin asset should have been announced. There would be no reason not to.
No, this closing of accounts sounds like a problem unrelated to a massive deposit of funds. In fact, there's no proof of any bank closing a USEI account. Just Tony saying so.