Complex sentence: As the couple begin to fight, Captain America enters bearing a letter addressed to the "Make A Christmas Wish With the Avengers" program, in which the members of the team reach out to child in need for the holidays.
Split into simpler sentences: As the couple begin to fight, Captain America enters bearing a letter. The letter happens to be addressed to the "Make A Christmas Wish With the Avengers" program, in which the members of the team reach out to child in need for the holidays.