There's multiple ways in which medieval Europe was affected by the three invasions, all coming from different sides, with different strategies and different goals.
The Viking invasion was both positive and negative, the positive being the accumulated knowledge about sea travel and ship construction, the negative being the occupation of important trading spots.
The Muslim invasion in general contributed to bigger unity among the Christian countries in Europe in order to preserve their religion and culture.
The Magyar and Szekely invasion contributed physical cultural separation of Central and Western Europe with the Balkans, but was positive for multiple smaller groups of people that were remnants of earlier empires, like the Avars, Huns, Kumans, who were incorporated into the new country and managed to survive on the European soil.
