the attitude of U.S. law to anonymous transactions

I just read a sentence as follows.

"The U.S. Department of the Treasury last month banned American citizens from interacting with the app, which allows users to anonymously send and receive Ethereum."

You and I installed each a geth(Ethereum's node). You and I can exchange Ethereum anonymously. Is this also prohibited under U.S. law? For reference, such acts are not prohibited in principle in Korea. It is prohibited only for business purposes. Thank you in advance.