Unity was brought mainly by the decades-long process of setting up and expanding the European Union in the aftermath of WW 2; also the disappearance of the Iron Curtain in 1989 was a major factor in uniting Europe. Major disruptive factors were of course the two World Wars, and before 1989, the existence of a Communist-dominated Eastern Europe versus Western Europe.
The Crusades brought much riches to Western Europe and created a sense of religious unity.
Charlemagne helped cause the unity in Europe by trying to have everyone unite through the religion Christianity. (There are some more factors in what united Europe, but that was all I could find.)
The Moguls.
The Magyars attempted to destroy ethnic identity, unity and peace.
Eastern Europe does not seek anything from Western Europe other than political unity and aid.
Crusaders brought back information from Muslims to Europe Crusaders brought ancient texts from Muslim libraries to Europe Crusaders brought back ancient texts to Europe.
Crusaders brought back information from Muslims to Europe Crusaders brought ancient texts from Muslim libraries to Europe Crusaders brought back ancient texts to Europe.
The Magyars attempted to destroy ethnic identity, unity and peace.
The Spanish brought guinea pigs from their colonies in South America to Europe.
No Pineapples and potatoes were brought to Europe in the 1600's
Unity and stability.