Some books are still banned in the US. With the ban very seriously enforced.

Anything that can be labelled as making fraudulent medical claims is in that category - the laws used to pulp Wilhelm Reich's books and send him to die in prison.

And national security is a useful excuse for anything else political. The US government's case against The Progressive ultimately failed, but the ban on the official Iranian transcripts of documents found in the American Embassy when they occupied it still stands.