The whole vibe of this thread is: "America does it this way, why does the international body do it another way? Obviously the American way is superior and everyone should do it the American way" which is just....
I didn't have time to read the entire thread and therefore didn't feel I had any right to comment, but my thought when I read the title was that the OP is asking the wrong question. The question should be Why doesn't USFSA have age limits on junior/senior when ISU does.