Well when Britain joined in 1973, it was meant to be purely a trading block - you know, no tarrifs, NAFTA was modelled on the original EEC.

What has happened is not similar to the American situation.

A better analogy would be if NAFTA suddenly became a federation - and without referendums, it is all agreed behind closed doors by "elites". When people have referendums saying "no", like the French and Dutch did over the Constitution Treaty, they just repackaged the exact same thing and forced it through as an amendment to existing treaties, which magically didn't require referendums (because supposedly "only" an amendment!).

Anyway - suppose this NAFTA monster is gaining all sorts of power, without the consent of voters. It starts to topple elected govts (see the way the Pappandreau govt in Greece and the Berlosconi govt in Italy were toppled by the EU, and unelected eurocrats (who were all ex-Goldman Sachs) were appointed Prime Minister. Even where there have been elections, like the Syriza govt in Greece, Brussels attitude was "how dare you defy us", and the ECB, which is a central bank that is supposed to have the duty of keeping banks open, shut down the Greek banks, in order to force the elected Greek govt to cave to Brussels (which they did).

In Ireland, the ECB over-reached itself again, sending threatening letters to the irish govt forcing them to do a bank bailout. The bailout was so big they needed IMF help, and of course austerity. The whole of the Eurozone benefitted from that bailout, but only the Irish taxpayers have to bear the brunt of the cost. At least with the bailout in the USA, the whole nation bore the cost, it wasn't just loaded all onto Conneticut. Americans complain about the Fed -but when was the last time the Fed threatened a state and said they'd close down their banks if they didn't enact certain policies (which should be up to the legislators not the central bank)?

The Irish govt now has to submit it's budget to Germany for inspection before they announce it to the Dail and the Irish people. Does Texas have to submit it's budget to New York first before it announces it?

Oh and did I mention confiscating savings? That's what happened to Cyprus without warning. They hadn't even done anything wrong - they had lent Greeve money, but the EU suddenly changed the rules on them.

So suppose you had this NAFTA monster, it is ignoring basic democracy, unelected authoritarians are running mad, there is no accountability at all.

Britain, which had refused to be part of the euro, thought, "You know what, we didn't fight a World War to be forced to submit to crap like this, we're out of here".

The EU is trying to make Brexit as hard as possible. The thinking is "we must punish them, so others arn't tempted to leave". A bit like the Soviet Union, right? If you need threats to make people stay, you have a crappy set-up. Britain isn't afraid though - not much frightens us after all this time.