Bob:

Below is an excerpt from an article titled What Happens if H.R. 1 Conflicts with U.S. Tax Treaties?
by Erika K. Lunder, Legislative Attorney, for the Congressional Research Service, dated December 19, 2017. 

I found it on the internet.  If it is on the internet, of course it's correct....

” The U.S. Constitution provides that the Constitution, acts of Congress, and treaties are 'the supreme Law of the Land . . . .' When the Constitution conflicts with a federal law or treaty, the Supreme Court has held that the Constitution is controlling...." 

Now, bear in mind I'm NOT an attorney.  Nor am I interested in researching further, beyond the freebie I got from the internet.  If I were to research further, I would go straight to the horse's mouth, i.e. the constitution, Constitution Annotated, and then the related explanations and/or case law.

For tax research, what better horse's mouth than IRC and the regs?  That was how I learned it from way back when.  In fact, I was drafting a response about how Section 9042 of the American Rescue Plan Act of 2021 referred to Section 85 of the IRC, and how the exclusion was added as Section 85(c).  I got to the part of "also check the treaty" when I saw the subsequent posts, and decided NOT to post mine.  Had I posted it, I would have been a Snide Bother of your...

Anyway, short story long, Bob, I disagree with you on you saying, that Treaties are the Law of the Land.  To me, conceptually, treaties are binding agreements between the U.S. and the signing countries.  The power to sign the treaties is a function co-handled by the three (mostly two) branches, and should still be subject to the Constitution.  Imagine a crazy situation when a treaty traded away our basic rights.  I don't think the Constitution would allow it.  But then, conceptually.

Just my 1.8 cents.  (Used to be 2 cents, before the market opened today.)