65% of US adults believe the Christmas story is literally true.
Interfaith post
Pew Research
This is an excerpt from the middle of the link.
The new survey also suggests that most Americans believe that the biblical Christmas story reflects historical events that actually occurred. About three-quarters of Americans believe that Jesus Christ was born to a virgin, that an angel of the Lord appeared to shepherds to announce the birth of Jesus, and that wise men, guided by a star, brought Jesus gold, frankincense and myrrh. And eight-in-ten U.S. adults believe the newborn baby Jesus was laid in a manger.
In total, 65% of U.S. adults believe that all of these aspects of the Christmas story the virgin birth, the journey of the magi, the angels announcement to the shepherds and the manger story reflect events that actually happened. Among U.S. Christians, fully eight-in-ten (81%) believe in all four elements of the Christmas story. Even among people who are not affiliated with any religion, 21% believe all these events took place, and 37% believe at least one (but not all) of them occurred.
http://www.pewforum.org/2014/12/15/most-say-religious-holiday-displays-should-be-allowed-on-public-property/