Here's something Maverick Philosopher would definately regard as a reductio of the democratic ideal: Jonathan Freedland, writing in the Guardian, suggests that we should all have a say in the US elections. And he makes a very good case: America's hegemonic power is so great that their decisions affect everybody on the planet. But by the very principles their revolution was founded on - people having a say in the decisions which govern their lives - non-Americans should now have a say in their "internal" elections.
No-one for a moment expects this to happen. But it's a nice idea how the ideals behind democracy - of everyone's interests counting equally, and having to be taken into account in any decision which affects them - undermine the Westphalian doctrine of national sovereignty.