Christianity is one of the classic Abrahamic monotheistic religion and has been around for so long
It also has a lot of similarities with other major religions.
yea its also the biggest religion, with 2.4 billion followers
I believe Atheism is a steadily growing thought process as well.
Yea while Christianity makes up a majority in over a 158 countries and territories Atheism seems to keep growing
Which country currently has the most Christians?  I would imagine it would be somewhere in Europe or the Middle East.
While Christianity makes up so much of majority of populationgs it probably has one of the largest in America 
I saw a video of Sam Harris speaking at a church with a pastor.  It was very interesting.  I recommend checking it out on YouTube sometime.