Why is catholicism widespread throughout the world.?

Good question. It is well doented that the Catholic church was the first Christian Church, so for many, many years in order to be Christian you would have to be Catholic. After the Romans embraced Catholicism they spread it though out most of Europe. Many of the Barbarian tribes or people then became Catholic Christians. And into England, again, with the Romans. And so the explorers that came to the new world were for the most part Catholics. From Spain, Italy, Portugal and others. Etc.