Modern day EU, is a sharing of power structure over the EU between France and Germany. The institutional seats for the EU are in Brussels, Frankfurt, Luxembourg and Strasbourg. Poland and the UK wanted Turkey to join the union to provide voting balance against Germany and France. This didn't happen and France made it clear that they'll never agree to it. The UK left because of this imbalance (despite having special privileges).
One way to think about the current EU in medieval terms: A personal union between France and Germany; and a bunch of associated vassal states.