Agents of SHIELD's season 7, episode 4 dropped two references to the events that took place in The Avengers, the movie that launched Coulson's SHIELD story. A pivotal scene in the 2012 Marvel movie saw fan-favorite character Agent Coulson (Clark Gregg) die at the hands of Loki (Tom Hiddleston). Following his shocking death, Marvel resurrected him to be the lead character in Agents of SHIELD, the first TV show tied to the MCU.
In Agents of SHIELD season 7, episode 4, titled "Out of the Past", the LMD Coulson and the SHIELD team are in 1955 when they realize that a key moment in SHIELD's history is about to take place. Apparently, the death of Agent Carter's Daniel Sousa (Enver Gjokaj), is right around the corner, which presents a big dilemma for the team, who are fully aware of the dangers that come with time travel. Finally, they decide to take the risk and change Sousa's fate. After developing a plan that will hopefully avoid potential consequences, Coulson and the others succeed in faking Sousa's death. Afterward, they take him aboard him the Zephyr, where Sousa joins the SHIELD team.
In dealing with their Daniel Sousa problem, two references to The Avengers were made. When discussing what might happen to SHIELD's history if they save Sousa, Mack (Henry Simmons) compares the impact of what happened to Sousa to how Coulson's death motivated the Avengers to save the planet. After Sousa is rescued, Coulson says, "welcome to life after death. I'll tell you all about it". Once again, this is a nod to Coulson dying in The Avengers, as he knows first-hand what it's like to be alive when you're supposed to be dead. He may also be referring to his experience as an LMD as well, since Coulson has now died twice.
Agents of SHIELD has acknowledged major events in the MCU in the past, with one of them, the fall of HYDRA in Captain America: The Winter Soldier, playing an integral role in the direction of the series. This time, SHIELD is taking a look back at what started it all. Coulson dying in The Avengers and the mystery surrounding his surprising resurrection served as the foundation for the show's story.
The connection between Coulson and Sousa is appropriate though, because there are strong parallels between their situations, even though Coulson's had nothing to do with time travel. As Mack pointed out, Coulson's death - as tragic as it was - helped the Avengers do what needed to be done and stop Loki. And to this day, the Avengers still don't know that Coulson was brought back to life. So for the characters in the movies, Coulson stayed dead. That's not unlike their concerns for the timeline with Sousa in Agents of SHIELD, since the loss of Sousa motivated the organization in the 1950s. Yet again, a SHIELD agent was fated to die, and his death was undone and kept a secret from everyone but the members of the team.