Political union means transferring the prerogatives of national legislatures to the European parliament, which would then decide how to structure Europe's fiscal, banking, and monetary union.
Why was there so much work-sharing in the 1930s? One reason is that government pushed for it. In his memoirs, President Herbert Hoover estimated that as many as two million workers avoided unemployment as a result of his efforts to promote work-sharing.
The consequences of a collapse would not be pretty. Whichever country precipitated it - Germany by threatening to abandon the euro, or Greece or Spain by actually doing so - would trigger economic chaos and incur its neighbours' wrath.