I fail to see what matter of the UN has any power over the U.S.
The U.N. was brought into being in 1945 to bring together the Nations to a debate-like society to prevent Wars.
How did the U.N. has grown to the point that it has law/treaty making power to tell the Nations such as U.S. what to do?
I have always believed that the U.S. Constitution is the Supreme Law of the Land and none of any other powers has any say how we govern our own country!
That would be correct. Treaties cannot modify or repeal black-letter law written into the U.S. Constitution.