The European Union functions more like the UN than the U.S.

And in the present situation in regard to Greece this could destroy the trust between European Union Nations.

For example, Imagine here in the U.S. one of the states that wasn't as rich as the rest running into this kind of trouble. There are mechanisms here in place in the U.S. to handle things like this because we have been a country of many states (From 13 to the present 50) since 1776. So, we have adapted to dealing with these kinds of problems over time.

However, the European Union has not come to this point because each country is a nation and not a state like in the U.S. Each country is still basically that same country it always was and the only real thing that they all share is the Euro and not much else in the end.

So, if the European Union is abusive to Greece (like they have been) then other countries in the EU can expect the same sooner or later. Who wants to be abused like Greece has been? No one.

If this results in mass starvation in Greece  with all the banks permanently closed I think you are going to see nations one by one leave the European Union over time.