After World War II, European integration was seen as an antidote to the extreme nationalism which had devastated the continent. It was natural that mitigation actions should be found to save Europe and its population. Already in 1946 Winston Churchill postulated the emerging of a United States of Europe during the 20th century. In 1952 the European Coal and Steel Community was formed and was a declaration towards the first step for the federation of Europe and the gradual build up of Europe towards full industrialization and technological progress. Thereafter in 1957, Belgium, France, Italy, Luxembourg, the Netherlands and West Germany signed the Treaty of Rome, where the European Economic Community (EEC) was created with the establishment of a customs union as trade is among key socio-economic issue to gain maximum market yields post the industrialization and technology advances. At the same time another pact was created, the European Atomic Energy Community (Euratom) for co-operation in developing nuclear energy. This is again a natural step in further developing the social-economic programs in Europe, as energy resources are strategic and imperative drivers. From 1967-1973 the European Communities were formed with the enlargement to include Denmark, Ireland, and the United Kingdom. In 1981 Greece joined, Portugal and Spain following in 1986. 1985, the Schengen Agreement paved the way for the creation of open borders without passport controls between most member states. In 1986, the European flag began to be used by the EEC and the Single European Act was signed. These steps are key issues of importance for trade, mobility and integration in the larger inner market in Europe, also for the international protection of the European trade-market.
After the fall of the Eastern Bloc in 1990 ((https://history.state.gov/departmenthistory/short-history/berlinwall), the former East Germany became part of the Communities after the reunification of Germany. With further enlargement to include the former communist states of Central and Eastern Europe, as well as Cyprus and Malta, the Copenhagen criteria for candidate members to join the EU were agreed upon in June 1993. This expansion of EU introduced new levels of complexity and discord especially as historical conflicts have to be resolved. With this, the European Union was formally established by the Maastricht Treaty (1992–2007), whose main architects were Helmut Kohl and François Mitterrand. The treaty also gave the name European Community to the EEC. Austria, Finland, and Sweden joined the EU in 1995. In 2002, euro banknotes and coins replaced national currencies in 12 of the member states. Then, the eurozone increased to encompass 19 countries and in 2004, the EU saw its biggest enlargement when Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia joined the Union. In 2007, Bulgaria and Romania became EU members. The same year and the following years, Slovenia, Cyprus, Malta, Slovakia, Estonia, Latvia and Lithuania adopted the euro. On 1 December 2009, the Lisbon Treaty entered into force and reformed many aspects of the EU, e.g. the legal structure of the European Union, strengthened the High Representative of the Union for Foreign Affairs and Security Policy. Both the introduction of the euro and expansion of Europe were further steps towards building the new identity of the larger Europe.
However, new realities emerged since the global economic crises of 2007-2008 (https://en.m.wikipedia.org/wiki/Financial_crisis_of_2007–2008) also from the beginning of the 2010s where the cohesion of the European Union has been tested by several issues. Including a debt crisis in some of the Eurozone countries, increasing migration from the Middle East, as consequences of wars and civil instabilities, and the United Kingdom’s withdrawal from EU ”Brexit” (https://en.m.wikipedia.org/wiki/Brexit). The UK formally notified the European Council to leave on 29 March 2017. Also, the 2016 elections in USA with the new political reforms by President Trump aiming at Making America Great Again have feedback impacts on the international socio-economic politics.
Catalonia is now calling for independence from Spain (https://www.theguardian.com/world/2017/sep/20/spain-guardia-civil-raid-catalan-government-hq-referendum-row) which already indicating, as in the case of Greece, regional economic insecurities can pile to trigger not only political instabilities but further large-scale and long-term economic consequences for both Catalonia and Spain.
(http://www.aljazeera.com/news/2017/09/spain-economy-survive-catalan-secession-170930163702214.html; http://money.cnn.com/2017/09/29/news/economy/catalonia-independence-spain-economy/index.html). From the viewpoint of the richer Catalonia and its population, the socio-economic developments in Spain as a whole can not be sustainable by being dependent on Catalonian economy forever. For both Spain and Catalonia a long-term solution has to be found as the situation is indeed getting much serious and the risk is that such scenario can have spillover effects to other parts of Europe.