Is the world segregated by religions? At all? Is it worth fixing, or trying to make better? If so, then how?
In my opinion, the world is somewhat segregated by religion, but in most places there are also minority religions. Minority religions are protected by the First Amendment to the US Constitution in the United States. The degree of tolerance of minority religions covers the spectrum from complete tolerance in the US to other countries that have state religions.
In the Western Hemisphere Christianity is the majority religion, and the same goes for most of Europe. Israel is of course predominantly Jewish at present, but in Jerusalem three major religions contend that sacred places exist in that city in Israel. The three religions are Judism, Islam, and Christianity.
The Hindu religion predominates in India. Shinto in Japan. And various types of Buddhism exist in the Far East.
But all these areas seem to have minority religions present. I really don't know if any other religion could openly practice it in the more strict Islamic countries.
From the beginning of time it seems that more killing has been done in the name of religion than any other factor.
Anything this serious is worth fixing or trying to make it better, but I can't imagine how that could take place. People live all over the world and have different religions. I can't see how we could move people around the world to reach a pro rata proportion of each religion across the face of the earth. Likewise, I don't believe you can change most people's religion anymore than you can force a form of government on people, as the US has attempted to do in various places around the world--most recently in Iraq.
The only way to improve this situation is tolerance of all or no religions across the face of the earth. People who are tolerant of other people's religion, form of government, etc. don't fly planes into large buildings of another part of the world. Tolerance would seem to be very difficult to accomplish in people who are willing to kill themselves to attack people who don't share their beliefs. I suppose that missionaries could go to Islamic countries and attempt to convert them to Christianity. This has worked to a degree on primitive people that have only local religious rites. I fear that if the same thing was attempted, their would be a whole new crop of Christian martyrs.
The only answer I can come up with is tolerance on behalf of the whole world, and leave each other alone to practice their religion, while the US respects all religions.
This is probably one of those problems that God is going to have to sort out.