Spain brought the Spanish-speaking countries the Catholic faith. Up until 1978, you weren't allowed to be a citizen unless you were Catholic. YOur marriages could have only been Catholic, etc. Spain is a zealous country and the other countries stuck with it's faith.
Spanish speaking countries speak Spanish because they were part of the Spanish empire. At the time of the conquistadors, Spain was a catholic country. Monks and priests often followed on the footsteps of the conquerors to convert the natives. Basic world history.
the Spanish cleansed Spain of all non-catholics during this time, they were at that time also a massive seafaring country, and saw it as their mission to spread the faith of Jesus Christ.
they murdered and pillaged many parts of hate worlds, subjugated them in colonies and 'raised' the inhabitants to be Christians.
Because the Roman Catholic Church used fear, subversion, torture, Spanish superstition, and murder to ensure the conversion of Spanish-speaking souls. Then, those converts raised their children Catholic, who raised their children Catholic, etc.
Because when Spain started exploring in the 1600's and taking over various areas where only natives existed, they brought their religion with them which was Roman Catholocism.
Because during the Age of Exploration the Spanish decided to go, well... explore. Spain's only religion at that time was Catholicism (as they had kicked out all Jews and Protestants). Their main goal in settling the New World was to spread the Catholic faith. King Phillip II even considered himself "the Defender of the Catholic faith."\
But fun fact: the country with the highest population of Catholics is Brazil, where they do not speak Spanish but Portuguese.
Spanish culture has not left Latin America -- the Spanish conquerors did their job thoroughly and the culture that is there (since 500 years) IS in fact the Roman Catholic-based Spanish peninsular culture -- with 500 years of separate history and changes.
It is truly a fascinating study of cultural interaction.
This is because the Spanish never separated form the roman Catholics like some of the other European countries did. So when they came to explore the new world as the first group to real do this they brought the beliefs that they had. This is also why most New England countries are not Catholics their country that people came form were not Catholics
they are hard core followers, who are easily swayed. so when the church says centuries ago, believe in us or we will ac use you of heresy, they said, OK.
Spain as part of the original Roman empire, embraced Christianity from the beginning. During the colonial period, imperialistic Spain, colonized many parts of the world and brought their religious faith with them.
The Spaniards and Portuguese who came exploring were thoroughly and enthusiastically Catholic. They taught Catholicism to the people they found.
Those people taught it to their children, and their children taught it to their children ... down to the present day.
Many people are more comfortable worshiping as they have been reared rather than investigating other forms of worship. People in Spanish-speaking countries are no exception to that custom.