The USA is not much smaller than the EU in population. One of its states alone has a much larger economy than most EU countries. Apart from the UK, twenty miles offshore, and islands that are not separate nations, the EU nations are pretty much a contiguous block. The US has Hawaii and Alaska, making the country less contiguous than the EU. There are tensions in both the EU between poorer "southern" states and the more prosperous "north." There is free movement of people in both. There are no tariff barriers between states/nations in both. The nations/states in both, crucially, are fiercely proud, to a greater or lesser extent, of their distinctive identities and are generally successful in maintaining them. In both, the nations/states enjoy a fair degree of autonomy whilst having to abide by laws that cover the whole lot of them. In general, these laws are overwhelmingly accepted by everyone, and representatives from all nation states/states have a say in making those laws. In both, there will be disagreements about some of those laws, but substantial disagreements are few and far between. There are plenty of differences between the two blocks, regarding language barriers and the origins and evolution of the two unions, and there's the disease of gigantism that afflicts both. But there are plenty of similarities, and Joe's comparison stands. It behoves us to examine what it is that works in each and to be informed by that.