At its core, Call of Duty: Modern Warfare 3's Passenger and No Russian have the same narrative purpose, with Makarov trying to use the attack to incite a war.
Taking place just four missions into the game, No Russian sees players take control of an undercover U.S. Army Ranger as they try to infiltrate Makarov's Ultranationalist cell. In order to gain favor with Makarov, players participate in a mass shooting in a Russian airport.
It's very scary, but not that graphic; occasionally a character will get shot or harmed by another, but most of the violence in The Terror comes from nature: dying from a great fall, for example, or being frozen alive.