Why is Europe not unified in history?

One of the reasons is that religions are different, and Europe seems to believe in God. As for Catholicism, Christianity should have deep roots. As far as I know, it's very different, and so is the doctrine. After listening to a lecture on history, I also mentioned that many wars in Europe in the past were related to religion, and some Christian countries invaded Catholic countries and killed them as pagans.

I also think it's the Pope. Europe was relatively unified during the Roman Empire. Later, when the Germans entered, it became the conquest of advanced culture by cultural lag. The Germans adopted the clan system, followed by the fief reform, which gradually split. Besides, the Pope does not want European countries to unite for their own interests.

Western Roman Empire, Frankish Empire, Holy Roman Empire

These are nominally unified western Europe.

If you count Northern Europe ... Before the Teutonic Order expanded northward in 1200, Northern Europe was always regarded as a wild land and was excluded from the world. Barbarian Berbers occupied the Iberian Peninsula in the west for 800 years, the Byzantine Empire with IMBA in the east stood for more than 1K years, and the Pope in the south.

In this way, the three empires unified Europe. Because even in China, the so-called unification does not include all places influenced by China culture.

It was the Visigoths who overthrew the Roman Empire. The Pope doesn't have that much influence. Historically, nobles often beat the Pope.

The Germans split because Charlie divided the Frankish Empire equally among his three sons, and then English, French and German began to appear.