How did powerful european states respond to the growth of nationalism during the 19th and early 20th centuries?

By aggressively suppressing nationalist movements (apex)

The growth of nationalism during the 19th and early 20th century had several consequences, but the most relevant were: the inevitable collision between nationalist states that wanted to have control on territory and population that speak the same national language (like the Franco-Prussian war in 1871); the collapse of big European multinational states (like the Austro-Hungarian Empire after WWI); and the rise of extremist nationalist ideologies that took control of many powerful European states.

Under these circumstances, the way in which powerful European states responded to the growth of nationalism can be divided into two fronts, first, there were some relevant states that embraced extremist nationalist ideologies and eventually were ruled by its premises and an offensive foreign policy towards its neighbors, like Fascism in Italy and Nazism in Germany. And second, other powerful states, like the UK and France, did not align with extremist nationalism but rather remained under a liberal and democratic form of government and a more defensive position. In general terms, World War II was the final clash between these two ideologies.