From afar, over here in Australia, it seems really odd to see how you guys look over these processes.
It seems to me that there are other, more global options, that may not be seen in the US.
In Australia Holden is the GM "brand"
In China Buick is the GM "brand"
In Europe Vauxhaul is the GM "brand"
In South Africa and Middle East Chev is the GM "brand"
In the US, well that's entirely out of my understanding, but seems to me that you sure as hell don't need so many "brands" selling such similar content.
The local markets define what vehicles from the GM family are available and sold. For instance in Europe it's a tad harder to sell SUV and large family cars whereas in Australia it's harder to sell small cars (but getting easier).
I suppose what I'm trying to say is that the consolidation of brands in the US doesn't mean that the same brand that is successfully holding market share in another location can't keep using that name branding.