Many Americans instinctively favour the European Union because it resembles - from a distance - the USA itself. It's not surprising that the citizens of a successful federal superstate favour the countries their ancestors fled seemingly copying the model they adopted in the New World. The idea that Britain might leave the European Project has therefore been received with surprise by Americans of all political views – not just statists who favour fewer partners to deal with in their fantasy world where governments, not traders, drive trade.
Few Americans understand that the EU is an anti-democratic institution based on centralised economic planning. So far from being a proponent of "free trade" it is a protectionist zone behind tariff and non-tariff barriers. It may have a President (seven in fact) but it requires some study to realise that Europeans can't throw the rascals out as Americans can theirs. It may have a Parliament, and that Parliament may be elected, but it's not the legislature. It's a decorative talking shop designed to fool an inattentive majority of voters far too remote from the EU institutions to pay them any mind.
If we look at agriculture as an example the EU is pretty much a White First World racket to keep Third World farmers in poverty by subsidising European farmers who could never compete with them fairly. It then adds insult to injury by sending any food surpluses created by its rigged market to the Third World as "aid." Aid that might never have been needed if the recipients had been allowed to trade fairly in the first place!
When I was a partner in a pan-European law firm, I often heard my Continental partners speak of their farms and vineyards on the side. The Common Agricultural Policy allows Europe's rich to get subsidies for such "hobby farms" from ordinary European taxpayers - the very people paying the resulting higher prices for their food! If that were not obscene enough, consider the disgusting concept of "set aside"; paying farmers not to cultivate land in order to reduce supply and keep prices high. The "set aside" scheme ran from 1992-2008, when it was abolished because of shortages after two poor harvests. It has never been acknowledged to be morally wrong and might be reintroduced if surpluses returned.
In a world where hunger persists, I can think of few things more vile than paying people (including hobbyists and others who would never have been in business were it not for subsidies) not to farm in order to keep food prices high. Post set-aside, the EU still subsidises (sometimes imaginary) olive groves while denying access to its markets to Third World farmers who could otherwise have raised themselves honourably out of poverty while feeding Europe's poorer people more affordably! Either the CAP is a signal of the moral darkness at the heart of the European Project, or the Énarques who devised it have proved, as Orwell said, that there are some ideas so stupid only intellectuals can believe in them.
The EU is sui generis, thank God. However, as Americans insist on wrongly comparing it with the USofA, they must forgive me for pointing out it more closely resembles the USSR. If there is an American analogy for the Brexit debate, it is with the War of Independence, not the political miracle that followed. I am happy that the Washington Post has now published at least one piece that seems to show a glimmer of understanding.