To me, that would be equivalent to requesting for someone affected with bubonic plague be allowed to board a crowded airliner.
The 2001 cylinder was an ill-advised quick-fix to a temporary problem, and letting it in SKUSA should never had happened in the first place. You’ve seen the posts in the Shifter Karts section here, about the problems that arise when pushing a 2001 cylindered engine to the jetting limit.
Why should the other governing bodies that were smart enough to keep it at ’99 only do the same? More participants? It probably wouldn’t make much difference in numbers anyway.