Is Christianity a Western religion? Where did it spread from and to?
Christianity began in the Mid-East and spread from the Mid-East.
The coming of the Spirit on Pentecost took place in Jerusalem, not Rome or Athens, and many nations were there from all around Europe and Asia.
We typically base our understanding of the spread of Christianity on the missionary journeys of Paul of Tarsus. Our Bible addendum come with maps of the Mediterranean basin, with the routes of Paul’s journey laid out in three colored lines. These maps seldom detail the historical outgrowth of Christianity beyond the missionary efforts mentioned in scripture itself.
Within the first 200 years of the birth of Christianity the major centers of Christian populations were in Syria, North Africa, and Mesopotamia. Within that time the Christian religion had spread not only to Rome, but as far as India. Within 500-600 years, all manner of Christian communities were found not only across Europe, but as far as China as well (China may have been reached as early as the 2nd century).
One common misconception is that Rome was the first earthly kingdom to declare Christianity its official religion, but the kingdom of Armenia did so beforehand (301 AD), and Rome didn’t agree to drop persecution of Christians until 10 years later. If we are to define the Westernness or Easternness of Christianity by the first kingdom to declare Christianity, we would have to call Christianity neither Eastern nor Western.
Christianity was indeed successful early on in the Mediterranean, and therefore throughout Southern Europe, but this does not make it Western.