This is a good point, and I have an idea I want to toss out here- maybe what's really dangerous is to have a mutual defense treaty between a lot of states but still allow them to have separate diplomatic relationships.. so that a snafu involving one member state can blow up and involve a bunch of countries who didn't need to be involved. If there was a central agency speaking for all those states then there would be fewer ways for a disagreement to occur. So what I'm saying is that 20 small countries will a mutual defense treaty are much more likely to be involved in a war than one big country over the same area. I don't know if that's true or not- you'd have to do the number crunching to find out..