Although the argument can be made that the museums of a state benefit from the exchange of information between states, it is not the strongest position from which to seek funding. On a constant basis, there would be too great a burden and too much reliance on one state over time. On a rotating basis, there are complex management issues that result from moving the operation from state to another. The organization of conferences, communciations networks, and other activities to support a national collaboration are more complicated and expensive than most single state associations can readily shoulder. Most state associations are not yet staffed and the work would have to be rotated amongst individuals already committed as board members to the agendas of their own state associations.
Some mechanism is needed to maintain a rotation and monitor the work to be done.
A formal entity with a national mission and support base facilitates fund raising from a broad range of sources. Board terms and by-laws can ensure broad representation. Management can be more efficient and effective. The organization will require financial support to sustain operations, coming at least partially from the state associations. A formal organization is at risk of eventually working to sustain itself for its own sake rather than the benefit of its constituents.