Is there one answer to why things happen?
No, but there are 2 essential reasons for why things happen__Karma and levels of consciousness. When you see or hear things that are occuring, one of these is usually the answer.
Is there anything I can do to change anything?
Yes, you can affect a change on your own level of consciousness through the various ways I’ve mentioned on site and in my books. Anything else is not necessarily crucial to change the world, but can be of help to others. If the world needed changing, it would happen through the grace of God. This is the perfect place to change your Self, however.