Theory: The MCU Is Setting Up John Walker To Be Another Super Soldier
Although John Walker doesn't want to copy Steve Rogers, his lack of Captain America superpowers may lead him to get the Super-Soldier Serum.
The Falcon and the Winter Soldier sets up John Walker as the next U.S.-backed Super Soldier with his efforts to become Captain America's successor. Steve Rogers' retirement after the events of Avengers: Endgame put the legacy of Captain America into question, but Sam Wilson's decision to give up the shield helped the U.S. government secure their own version of Captain America: John Walker. Although John Walker is equipped with plenty of experience and innate talent, he doesn't have the two most important qualities that made Steve Rogers the definitive Captain America: humility and superpowers.
The history of the Super Soldier in the MCU has become increasingly complex. Besides Steve Rogers, characters like Winter Soldier, Red Skull, and the Abomination have had different variations of the Super-Soldier Serum, and all with a wide variety of negative side effects. The Falcon and the Winter Soldier episode 2 reveals that Isaiah Bradley was also a Super Soldier more than 70 years ago, though his existence was kept a secret. Everything seems to point out that being a Super Soldier is more trouble than it's worth, but that hasn't stopped new Super Soldiers from appearing.
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John Walker doesn't seem to have evil intentions. However, the path to take up the Captain America mantle is difficult, even more so under the shadow of Steve Rogers – and, certainly, John Walker is a different Captain America than Steve. This grueling responsibility could easily push Walker to seek a way to become a Super Soldier, and perhaps lose his humbleness in the process.
Walker already masters Captain America's shield throw, but that is not enough to take a Super Soldier's punch, fall off a moving truck, and spring back up to chase it on foot - something that Bucky Barnes and Steve Rogers could easily do. Despite John Walker's natural talents, he's easily overpowered by Karli Morgenthau and the Flag-Smashers. After his first defeat, John Walker must be about to realize that he really needs an extra push to follow in Steve Rogers' footsteps. Coupled with Sam and Bucky's refusal to cooperate, John Walker could conclude that a good attitude is only going to get him so far.
The Falcon and the Winter Soldier episode 2 also teases John Walker's first brush with fame and power, as he clearly loves the attention he gets from Captain America fans. Steve Rogers, on the other hand, never cared about his popularity. He chose to utilize his special abilities for the greater good even if it meant he had to break the rules or earn worldwide judgment, whereas John Walker prioritizes his public image and his relationship with the U.S. Government. In fact, there's no reason why the U.S. Government wouldn't want to have an obedient, superpowered Captain America now that Super-Soldier programs don't end up in catastrophic results like the unstable Soviet Super Soldiers or the misguided experiments that resulted in the creation of Hulk and the Abomination.
The Power Broker is namedropped in The Falcon and the Winter Soldier episode 2 when the Flag-Smashers are loading their cargo onto a plane, which suggests they got their Super-Soldier Serum from him without his permission. In the comics, the Power Broker is a villain who provides regular humans with superpowers. Unlike the volatile Extremis from Iron Man 3, the effects of the serum seen in the Flag-Smashers' fights prove that the Power Broker has successfully replicated Project Rebirth without negative side effects. This makes him John Walker's best option to become a Super Soldier.
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The U.S. Government could hire the Power Broker to provide John Walker with the same abilities as the Flag-Smashers, but Walker could also go rogue and negotiate with him personally. If he really wants to become the "new Captain America" officially, his lack of superpowers is a reason to worry. After all, facing one or more of "the Big Three" (aliens, androids, and wizards) on the daily is basically his job description. It's just a matter of time until John Walker finds himself enjoying Captain America's superpowers. Besides, the Power Broker may not be on friendly terms with Sam Wilson and Bucky Barnes, so his interest in helping replace Steve Rogers might also be personal.
The Falcon and the Winter Soldier episode 2 showed the difference between Steve Rogers and John Walker when the latter chose to use a gun on one of the Flag-Smashers to help Lemar Hoskins/Battlestar. Although Steve Rogers didn't have a strict no-kill rule, he would still have found a way out of the predicament without pulling a gun on his opponents as his first resort. Within the MCU, it's a known fact that the serum amplifies the attributes of its users, whether they're positive or negative. Hence why Steve remained a true hero while Red Skull became a supervillain, and why Dr. Erskine chose Steve Rogers over many stronger recruits in the first place. In the comics, John Walker, aka U.S. Agent, becomes a reckless version of Captain America, as he doesn't hesitate when he wants to punish his enemies. It's likely that the John Walker of the MCU will go down the same path, as enhanced abilities pave the way for overconfidence.
Neither the shield nor the Super Soldier serum guarantee that a new Captain America will be as heroic as Steve Rogers. Steve's most important quality is that he wanted to be a hero rather than act or be seen as one. John Walker could have the best of intentions, but as The Falcon and the Winter Soldier appears to be illustrating, power can really consume anybody. It could break Bucky's mind, let the government torment Isaiah Bradley, allow the system to give Sam Wilson the most basic level of respect only when he's an Avenger, and push John Walker to become Captain America's sinister counterpart.