The 2nd World War came to an end in 1945 with the surrender of Germany to the Allied forces. The infrastructure of many European countries lay in ruins. Most European countries were burdened by debt, were close to bankruptcy or were bankrupt.
Part or all of the populations of some European countries had been displaced by peoples of other countries and much of Europe had been taken over by Russia. Many millions of people were killed in local fighting while they were trekking back to their homeland and when the owners of property tried to recover their possessions.
Initially, during the war the USA had supported the allies by manufacturing and supplying essential military equipment to the allies and after Pearl Harbour by joining the UK in fighting Germany & Japan.
After the War the USA provided enormous financial aid known as “Marshall Aid” to many countries in Europe which enabled them to reconstruct infrastructure which included houses factories roads railways etc.
THE UK had been supported during the war by its empire. However, after the war there was substantial unrest in many countries which were of interest to the UK including the commonwealth countries. As an example, fighting broke out in Palestine when many displaced Jews wished to form Israel as their homeland, fighting broke out in Malaysia and Korea and the UK had to occupy its sector of Germany. The UK did not have the resources to fulfil its military commitments.
The UK had suffered from continuous German bombing for four years which was aimed at its manufacturing capability. The majority of German cities and factories had been destroyed by the allies’ military action and a high proportion of the German population had either been killed or were in prison of war camps. The currency, their businesses and banks had collapsed.
Russia had occupied the majority of Eastern Europe and threatened to take over the remainder of Europe.
Japan had surrendered as result of the atom bombs which were dropped on them by America.
China was a sleeping nation which took little part in international affairs. And the rest of the world together with the majority of the Commonwealth were recovering from their military support to the UK and on the whole had undeveloped economies.
Countries such as Argentina, Brazil, Chile and Peru had substantial commercial opportunities although their exports were relatively small.
You must decide if this is relevant, although it is true. After France had surrendered in World War II it cooperated with the German government although a small proportion of the population followed De Gaulle who supported the Allies. Italy entered the war with Germany although it sought an armistice when the British and German armies were advancing towards Rome.
After the war they joined with Germany to form the Iron Coal and Steel Community in 1951 which was followed by the European Economic Community (EEC) which, at the Maastricht Treaty, was renamed the European Union (EU) which the UK joined in 1973. Prior to 1973 the UK had not been invited to join or participate in the EU and therefore had been unable to support and participate in the development of the EU.
Under the Labour Prime Minister, Harold Wilson, there was a UK referendum on continued membership of the EEC in 1975. The electorate voted ‘Yes’ by 67.2% to 32.8% to stay in Europe. On the 23 June, 2016 a further referendum was held, to decide whether the UK should leave or remain in the European Union. Leave won by 51.9% to 48.1%. This showed a significant increase of the population who were now against the EU.