Why are so many countries concerned about the growing globalization of the media?

The media is a very effective socialization agent.
others being peers,schools and family.

The countries might be fearing the perceived negative effects on their societies and cultures, and the problem it may pose on social order. The media has the ability,especially the social media to be manipulated as instrument of war and propaganda.

Basically create a schedule on what you need to study and stick with it