@Wreford Brown;
I managed to have USAM in my GWX Merged Campaign plus Wilhelmshaven v7, but merging your MIS files (included in the "documentation" folder), with my three campaign layers (GWX plus Wilhelmshaven v7), with ME. The Museum works fine with all the new stuff visible, and new campaigns load normally (aprox. 9 minutes).
It seems my GWX plus Wilhelmshaven (v6 or v7) is diverse respect the included in your GWX direct installation folders (I donīt know what is the difference). Because that, I strongly recommend merge the campaign files with ME, with all the supermods, included GWX.
Many thanks for all the great work and the support!
Best regards.
Fitzcarraldo