Not even Steve Rogers a.k.a. Captain America (Chris Evans) could've survived the final snap in Avengers: Endgame. Even though neither film was the last entry in Phase 3, Avengers: Infinity War and Avengers: Endgame brought together the most significant characters in the Marvel Cinematic Universe for a culminating event. Not only did the movies feature exciting MCU crossovers, but the scope of the films was raised with the presence of Thanos (Josh Brolin) and his quest to rebalance the universe after obtaining all six Infinity Stones. Once he accomplished this goal, he snapped his mighty fingers, and fans saw the majority of MCU heroes turn to dust.
The snap played a massive part in the surprising ending to Avengers: Infinity War, but the act was even more prominent in Avengers: Endgame. The film showed two snaps with a third occurring off screen. Thanos snapped his fingers again between the movies to reduce the Infinity Stones to atoms, leaving a time heist as the Avengers' only solution to get the powerful stones for themselves. Once they did acquire all six Infinity Stones, Smart Hulk (Mark Ruffalo) snapped his fingers to bring all the previous snap victims back to life. Then, Tony Stark a.k.a. Iron Man (Robert Downey Jr.) made the ultimate sacrifice and snapped his fingers to wipe out Thanos and his army. While fans have mourned the death of Iron Man, many have also wondered how other MCU characters, like Captain America, would handle the power of the snap.
With his willingness to toss himself on top of a grenade before he had powers in Captain America: The First Avenger, there is no question that Steve Rogers would be willing to use the power of the Infinity Stones to save the day if need be. But that does not mean that the super-soldier could handle the snap's effects any better than Iron Man. Although Captain America is super strong and has an above-average recovery time from injury, he is still just a human. With all the previous snaps in the MCU, it is clear that using all six Infinity Stones in any manner will severely damage the user, and there's no reason to believe Captain America could have survived the snap.
In every instance that the Infinity Stones were used for a snap, the user was seriously damaged by the power that surged through them. Thanos was weakened in the aftermath of his first snap, but the toll of the second snap was clear in Avengers: Endgame. He moved much slower and had charred scars all over his right side. The benefit that Thanos had each time, though, was a proper Infinity Gauntlet to harness the power, as well as his alien (potentially Eternal) DNA. Meanwhile, Hulk explained that he was best suited to use the stones with the Stark Gauntlet because most of the radiation the snap releases is gamma. Although his origin is tied to gamma radiation, the power of the snap still knocked him out and severely damaged his right arm. As for Iron Man, he might just be a human, but he still had his nano-tech suit to protect him.
Theoretically, if Steve did use the Infinity Stones and took Iron Man's place at the end of Avengers: Endgame, it is clear that he would not have survived either. There is even an argument to be made that he could've died quicker since he wouldn't have a full-body protective suit like Tony. As fun as it is to think about what would happen if Avengers: Endgame played out differently, there is no question that the best ending was chosen for Captain America. He got to spend a lifetime with Peggy Carter (Hayley Atwell) and then pass on the shield to Sam Wilson (Anthony Mackie) so he can be Captain America now, starting in The Falcon and The Winter Soldier on Disney+. None of that would be possible if he had used the Infinity Stones, and it also allowed Iron Man to prove once and for all that he was willing to put his life on the line to save the world.
