In formal political groupings, countries pool their sovereignty and yield some autonomy in return for the benefits of greater collective power and increased stability. As Sir Winston Churchill said at the Congress of Europe in 1948:
“It is also possible and not less agreeable to regard this sacrifice or merger of national sovereignty as the gradual assumption by all the nations concerned of that larger sovereignty which can alone protect their diverse and distinctive customs and characteristics and their national traditions.” 
The EU gains many benefits as a result of its pooled sovereignty:
- It underpins peace in Europe – in contrast to the historical tensions which culminated in the two world wars of the 20th
- It has conferred collective citizenshipon its population, whereby people are free to move between member countries without restriction and without losing social benefits – although some people see this as a problem: allowing unrestricted immigration.
- The increased travel and interaction within Europe makes it less likely that people will regard other countries as hostile. People are becoming much more familiar with each other – grumbling from time to time, but nonetheless tolerant.
- Its members can exert more political influence in the world with a collective voice than they would each wield as separate countries.
- It enables businesses to benefit from free trade (22.214.171.124) within a single market.
- It extends financial support for the development of less prosperous regions, thereby reducing migratory pressures and social friction.
- It provides a legal framework (126.96.36.199), whose benefits include the enforcement of contracts and the coordination of crime-prevention and law-enforcement.
- It imposes human rights by law (188.8.131.52), as a condition of membership, to prevent politicians from abusing their powers in the way that Hitler did.
These benefits are not immediately felt on a daily basis, though; as described below, there is discontent (184.108.40.206). Many people are more aware of the costs and constraints than of the benefits.
 Sir Winston Churchill addressed The Congress of Europe on 7 May 1948, in a speech extolling the value of European unity. The full text of his speech was available in July 2018 at http://www.churchill-society-london.org.uk/WSCHague.html.