The history of the world is littered with the debris of empires: Roman amphitheatres, Inca cities, the great wall of China. Empires have been very successful in many ways. They have facilitated trade, travel and communication, they have enabled innovators and artists to work, improve lives and inspire people. The ancient Romans and Arabs influence our lives and cultures in many ways to this day. The British Empire was the latest and greatest in the procession, and it has shaped the modern world most of all, leaving many benefits around the world, not least parliamentary democracy and an independent judiciary in North America and India.
Yet empires are not something to wish for. Historically they have been forged by bloody conquest. Usually a people, led by ambitious generals and power-hungry leaders, attacks, subjects, controls and exploits other neighbouring or far-away peoples, mostly against their will. That’s if they are lucky. If they are not they will find themselves forcibly converted to an alien religion, with their language repressed, not infrequently accompanied by ethnic cleansing in the form of forced removal or straightforward murder and genocide (such as in the formation of the modern US). Not a pretty picture, and a high price to pay for railways and trade with the wider world.
The European Union is an attempt to create the benefits of empire: cooperation between neighbours, free trade over a large area, easy travel, order, prosperity and internal peace and security; without the bloody conquest and draconian repression. Uniquely, the EU is the coming together, by choice, of democracies in a larger formation which is governed partly by elected representatives of the member states, and partly by its own institutions, such as the elected European Parliament. It is based on the idea that you can have a large scale geopolitical entity without the domination of one culture over many others, without the persecution of minorities or the eradication of languages. Inevitably there will be tensions as such an organisation develops. The United States (which is a kind of empire, too) has always been riven by competition between the power of the individual state governments and the federal government. That is part of the checks and balances of the system. In the same way it is inevitable that there will be tensions in the EU between Brussels and the member states over many issues, perhaps sometimes leading to certain countries leaving. It is actually an important aspect of the nature of the EU that a country should be able to leave peacefully, because it underlines that this is a union of choice, and not one of coercion, both in terms of joining and staying in.