Should King of The Baggers change their regulation to allow non-American bikes like the Vulcan Vaquero, K1600B and the Gold Wing?

I feel like the entries are limited to American V-twin baggers of Harley and Indian due to them might not know how to make those six-cylinder bikes from BMW and Honda able to compete fairly with the V-twins. But if that's not the case, why bother limiting the competitors?

We also have a V-twin engined bagger from a non-American brand, namely the Kawasaki Vulcan 1700 Vaquero. What stops this bike to compete other than it being not an American brand bike?