I think Beaver Driver needs to look a bit more carefully at what the EU actually is. It is in fact remarkably similar to the United States. Some interesting points --
When the Declaration of Independance was signed and for many years afterwards the US did not have a common currency.
The EU has the powers to, and regularly does, pass and enforce laws that take precedance over national laws and regulations.
Individual US states can and do pass laws that are contradictory to the next one over. e.g. most US states do not have the death penalty or do not enforce it.
Kings and Queens are an irrelevance, they are figure heads and have no, or only theoretical powers.
There is free movement of residency and employment in the US.
There is free movement of residency and employment in the EU.
Each US state has their own flag.
Each EU state has their own flag.
When you move to a new state in the US you need to go to the local DMV to get a new driving licence.
When you move to a new state in the EU you need to send in your old licence for a new local one.
Car insurance in the US is valid in all US states.
Car insurance in the EU is valid in all EU states(sometimes third party only)
Each US state has thier own army/navy/and or airforce which is under the control of the locally elected head of state (Govenor)
Each EU state has their own army/navy/and or airforce which is under the control of the locally elected head of state (Prime Minister usually)
Every few years the residents of each state select a number of representatives to go to a Parliment and pass laws that bind them and thier locally elected Governments (both EU and US)
The EU has a judicial system that can, and does, overrule judgements made by individual states' judges. (eg European Court of Human Rights)
The US has a judicial system that can, and does, overrule judgements made by individual states' judges. (eg The Federal Supreme Court)
More to the point if any group chooses to give its right to negotiate to a body to do so collectively that should be their right, whether it is the EU or, for example, the Commonwealth. The only proviso should be that once an agreement is reached it is binding on all parties. You cannot give away your rights then decide the result of the negotiations does not suit you.