The Supreme Court ruled in the Head Money Cases that "treaties" do not have a privileged position over Acts of Congress and can be repealed or modified (for the purposes of U.S. law) by any subsequent Act of Congress, just like with any other regular law. The Supreme Court also ruled in Reid v. Covert that any treaty provision that conflicts with the Constitution are null and void under U.S. law.
The US Supreme Court ruled that treaties can be repealed or modified by what for the purposes of US law?
Act of Congress