How is it unconstitutional?
You have to start with the understanding that the ONLY source of legitimate federal government power is ONLY that which is delegated and enumerated in the Constitution which created the federal government.
So where does the Constitution give the feds power to regulate the American People proposed by this bill?
(This is not a treaty with a foreign government, it is a proposed US law. US laws MUST conform to the U.S. Constitution or it is an invalid and unenforceable law (US Const., Art. VI, Cl. 2).