This is the pertinent section.
No mention of North Americans or MNA's as far as I can see.


18. ISAF AND OTHER EVENTS
ISAF approval of World Championships and other Events
18.1 ISAF approval is required for any event that is described as a World Championship, uses
the word “World” in the title of the event, or any of the promoters, organizers or any other
organization officially connected with the event, represents or holds out in any way that
the event is a World Championship or does the foregoing in such a way that the event is
reasonably perceived to be a World Championship.
ISAF Classes (International and Recognized)
18.2 Each ISAF Class is automatically granted the right, subject to the notification requirements
of Regulation 18.10, to hold one annual World Championship.


ISAF Regulations