The way we make it work in the US is with federalism and huge ongoing cash transfers (poorer states get way more money out of the federal government than they p

The way we make it work in the US is with federalism and huge ongoing cash transfers (poorer states get way more money out of the federal government than they pay into it). Each of these alone are politically toxic in Europe, never mind both of them together; hence the increasingly widespread sense that the Euro is doomed in the long run.