The Swiss model is a fascinating one. The level of independence of the cantons is such that there are even arguments for considering the cantons to be almost sovereign states, and Switzerland therefore as an international federation. And of course Switzerland does this across the four-way language divide and a religious divide. The great unifing forces are:
1 Relative similarity in economic development of the cantons along with broadly similar fiscal and domestic policies.
2 Popular support for the idea of Swiss identity.
The EZ is totally lacking in (1) and has problems with (2). Right now Belgium, Italy and Spain have strong forces which tend towards breaking them up. There are plenty of people in Milan who don't identify as Italian, let alone as European. Italy is pursuing domestic spending which shows no respect for the needs of the EZ.
If the EZ does go for the single nation state solution then the euro crisis would be solved and the UK/USA would be very happy. But it would have to happen very quickly. IMO it just isn't possible on the timescale available, even if people in the EZ would support it - I just don't see this happening. Therefore the euro must fail. Sarkozy appears to be in denial. Indeed his policy seems to be keeping the euro going until after the French presidential election. Berlusconi seems more bothered by the supply of young women to satisfy his sexual excesses than the fate of Italy or the EU. Merkel seems to have a degree of sense. The Spanish press seems to have all but stopped reporting euro problems (maybe tucked in the business pages). Right now the key is that EZ politicians recognise that the euro will fail and manage the process.
By contrast the UK has a vote around 10pm where a lot of Conservative MPs look like rebelling. The biggest previous rebellion is 41. There is talk that this could be 60-100. There is a degree of expectation management from the government, but anything over 41 will be a victory for the pro-referendum lobby. This issue is going to come back again and again in UK politics. It will prompt a more Euro-sceptic policy, and a greater frankness by UK politicians in speaking out against the folly of the euro.