"Globalization is making the world smaller " This uses the present continuous because it's an ongoing thing (the world will continue to get smaller). "Cheap international flights have made overseas travel possible for millions of people." This uses the present perfect tense because it refers to a completed action/event (overseas travel was not possible before, cheap flights made it possible). I hope that helps!

Globalization /makes/has made/made/is making/ the world smaller. Cheap international flights /make/have made/made/are making/ overseas travel possible for millions of people. Depending on the context, all of the tenses are possible and could have very similar or very different meanings. Make/s - most general, less focused on current result or process. Have/has made - present result of something started in the past Made - in the past. Is/are making - focusing on current process. But from context we often already know the timeline and the results, so there could be multiple options to convey a certain idea - possibly with different emphasis. In isolation, the first statement is basically meaningless and the second is imprecise to the point of being meaningless. There’ve been millions of travelers for a long time.

is making -- process have made -- result