Despite all the horror stories of Brussels-based bureaucrats issuing edicts on what constitutes a tomato and other like regulations, the EU has been a huge success. In terms of combined GDP and population, the EU has a larger economy than the United States, at least on paper. Of course you can use a single credit card, but you always need a little money for some things. Multiple currencies in one trade zone are more than just an annoyance. The same six countries sign the Treaty of Rome, establishing the European Economic Community.
Initial emphasis involves dismantling of tariffs among member countries.
Eventually, EEC establishes a common tariff toward non-EEC countries. European Commission, responsible for harmonizing trade policies, is headquartered in Brussels. Essentially, each country can decide its own national interests, so this agreement significantly burdens EEC decision making for the next 20 years. Norway stays out following a referendum. Preparations for the euro begin.