It's how the Americans do things and it has got worse under Trump.
Anything involving US dollars and breaking sanctions will incur the ire of OFAC.
(edited for brevity)
Application Of U.S. Sanctions Laws To Non-U.S. Parties.
The U.S. sanctions typically apply to “U.S. persons.” However they can also apply to non-U.S. persons and companies in certain cases – and the incidence of and legal theories behind such applications are expanding.
The term “U.S. person” is generally defined in the U.S. sanctions laws as: (i ) U.S. citizens and permanent resident aliens wherever located; (ii) entities organized under the laws of the U.S. or a jurisdiction within the U.S. (iincluding foreign branches of such entities); and (iii) any individual or entity within the U.S.[ix] Also property of foreign parties that is located in the U.S. or comes within the possession or control of any U.S. person anywhere in the world is subject to OFAC jurisdiction.
In addition, however, OFAC has applied the sanctions laws to foreign companies in many instances as well. In fact, the incidence of this is increasing due to recent political events (such as in Iran and N. Korea), and recent legislative enactments such as the Countering America’s Adversaries Through Sanctions Act of 2017 (“CAATSA”).[x] To date there are four principal categories in which non-U.S. parties have been subject to U.S. sanctions: (i) where the foreign party has a requisite level of contacts with the U.S.; (ii) where the foreign party has been designated itself for sanctions and listed on the SDN List or other restricted party lists; (iii) under “secondary sanctions” (ie., sanctions that specifically apply to non-U.S. persons); and (iv) for providing material support or assistance to or facilitating a significant transaction with certain parties that are subject to sanctions. If a foreign company or individual violates a provision of the U.S. sanctions laws, they can be exposed to significant consequences for such actions.
A. Contacts With the United States.
To start, if a non-U.S. company has a sufficient level of contacts with the United States, it can become subject to OFAC jurisdiction and the U.S sanctions laws. Such jurisdiction can arise in a number of ways. If a non-U.S. company engages in a transaction involving U.S. persons or U.S. - origin products, technology or services, or has a presence in the U.S., the transaction can become subject to OFAC jurisdiction.
In addition foreign firms can be found to have “contacts” with the U.S. even if they only have a limited presence in the U.S. and there are no U.S. persons, products, technologies or services involved. The question of what constitutes a sufficient nexus to U.S. jurisdiction is an evolving theory of law and is expanding over time as new OFAC enforcement cases are announced. ...
OFAC has long held that if a non-U.S. company engages in business transactions in U.S. dollars, the foreign party is availing itself of the U.S. financial system and hence becomes subject to the U.S. sanctions laws. This is even if the company and the transactions are outside the U.S. Some of the largest OFAC enforcement cases have involved foreign financial institutions and their operations involving countries subject to sanctions ...
Foreign companies with the requisite U.S. contacts that engage in sanctions violations face potential OFAC civil enforcement actions and criminal prosecution by the U.S. Justice Department, and are subject to the penalties discussed in Section 1 above. ....
Thus even if a non-U.S. company has only tangential contacts with the U.S., it runs the risk of becoming viewed by OFAC as a “U.S. person” and/or otherwise subject to U.S. jurisdiction. Whether a company’s contacts with the U.S. rise to the level of establishing U.S. jurisdiction will depend upon the facts of the situation and the most recent OFAC enforcement cases. The question of what constitutes a sufficient nexus to U.S. jurisdiction is likely to continue to evolve as new OFAC cases are announced in the future.
B. Direct Designations For Sanctions.
At the core of the U.S. sanctions laws is the actual designation of a specific person or entity as a target for sanctions. If a foreign party engages in activities that violate specific U.S. policy goals, the U.S. can designate the party on the SDN List or target it for other types of sanctions. Since most parties designated under U.S. sanctions are non-U.S. parties, this can be a significant source of liability for foreign companies.
https://www.jdsupra.com/legalnews/u-s-sanctions-laws-dangers-ahead-for-74463/The bank might find itself declared an SDN and then it will become a pariah. No access to the Dollar transaction network....other banks with any US connection (ie use dollars) simply will not do business with it.
Most likely case - a very large fine.