I'd like to remind Loco that (discussed in post #23), there was no official alliance between GB and Black. It was voted down in GB because of the Pirate insistence they be granted both Baracoa and Port Antonio.
From my remembrance, many of us who thought it was a good idea anyway (barring the sticking point), were simply acting as if the terms had been agreed to.
I agree it was working pretty well while the US was riding high. Once they were beaten down a bit and thrown into disarray as a large clan moved from US to Pirates, however, it was a bit concerning to us who you would decide to fight, after they had collapsed. I assume plans were being made in case things changed, and the de facto alliance fell apart.