Captain America's Endgame Choice Created a Dangerous New Reality

Following the universe-altering events of Avengers: Endgame, Steve Rogers took on the crucial task of returning the six Infinity Stones to their proper moments in time. His mission was to clip every branched reality the Avengers had created. But he made a personal detour that changed everything, choosing to remain in the past and finally have that dance with his beloved Peggy Carter.

A Tale of Two Timelines

This decision has sparked two major theories about its impact on the timeline. The first, supported by directors Anthony and Joe Russo, suggests that Rogers created an entirely new, alternate timeline. In this reality, an older Steve lived out his days with Peggy while his younger self remained frozen in ice, waiting to be discovered in the 21st century. This means for decades, two versions of Captain America existed at the same time.

The second theory, favored by the movie's writers, proposes a closed loop. In this version, Steve was always Peggy's mysterious husband, fulfilling his destiny within the main Sacred Timeline. However, this idea creates a paradox, leaving the fate of the younger, frozen Steve unexplained. Because of this complication, the branched timeline theory is generally seen as the more plausible explanation.

The Incursion Conundrum

The creation of a new timeline isn't without its dangers. The Ancient One warned Bruce Banner that removing an Infinity Stone from its reality leaves that universe vulnerable to attack from dark, mystical forces. This catastrophic event, known as an Incursion, involves two realities colliding and destroying one another. While Steve returned the stones, his very presence in the past created a major deviation.

By choosing to stay, he created a timeline that was never meant to exist and couldn't be clipped. The existence of two Steve Rogers in one universe for such a long period—from the 1940s until Peggy's death in 2016—could have introduced a fundamental instability into that reality's fabric. This makes his new home a prime target.

A Hero's Choice, A Universe's Price

This instability could serve as a gateway for an Incursion. A weakened reality is an open invitation for powerful villains from across the multiverse, like Doctor Doom, to invade and conquer. What seemed like a selfless hero's well-deserved reward might have planted the seeds for a multiversal war.

Therefore, Captain America's simple, heartfelt choice to be with the woman he loved could have doomed an entire universe. The full consequences of his decision have yet to be seen, but they could be far more devastating than anyone imagined.