Every year about 8,000 people file their cases for cert at the Supreme Court. Each year they grant cert on about 80. Roughly 1/1000 odds. Those about 8,000 cases include cases that have also previously filed in past years without cert.
Amicus briefs are not uncommon. They often don't grant cert when there are no novel legal questions. The Supreme Court simply doesn't not have the ability to hear every appeal. Them not grant cert in any case should not be taken as a dispositive.
America and Americans broadly do not respect "international law" as an idea. We don't vote for representatives in a UN House of Reps or UN Senate. And if we did why would we wish to be beholden to a majority rules vote when that majority combined might be inferior militarily.
America tolerates international law when it doesn't interfere with our course.
The idea of a "one world government" is treated as a fringe tin hat conspiracy theory nonsense that no one is advocating for.