Here are a few points for your answer.
1. The rise of nationalism in Europe can be traced to the French Revolution. The French revolution ended the feudal system and created a strong sense of nationalism in Europe.
2. Nationalism spread all over Europe following the French Revolution. The middle class in Europe began to view nationalism as a liberal right. They wanted to end feudalism and monarchy in Europe and establish a system of popularly elected governments.
3. In the economic sphere, nationalism began to be interpreted as free trade and free movement of goods and capital.
4. Conservative governments like Prussia, Russia and Austria sought to resist nationalism in their countries.
5. But by the middle of 19th century, nationalism had gained strength in Germany and Italy where nationalists sought to unify these countries. This eventually led to the unification of Germany and Italy in 1871.