It's just silly. These coaches aren't making significant 6 figures, so financially, it's stupid to move when the job doesn't have high security, and many wouldn't want to be away from their families too. You can have a main hub in smaller countries in Europe because they are the size of a single state, but it's impossible to do in the US without eliminating many candidates who just won't bother getting involved.
To me, you have to break it down by region. And to act like you can't have those regional teams playing the same style and coaching the same way is just absurd.