America Chavez, played by Xochitl Gomez, was introduced to audiences in Doctor Strange in the Multiverse of Madness, a character who curiously existed in just one timeline. The multiverse is at the heart of the Marvel Cinematic Universe’s Phase 4 schedule, and likely beyond. Doctor Strange 2’s post-credit scene revealed that its hero had accidentally started an incursion – a multiversal collision – which was vital in this. It also debuted America Chavez, the MCU’s first completely multiversal superhero.
After learning that America Chavez possesses the ability to leap between universes, Scarlet Witch got obsessed with her. America’s abilities are barely under control – they were first awakened when she was stung, leaving her two mothers stranded somewhere in the multiverse – but she gained confidence and ability throughout Doctor Strange in the Multiverse of Madness. It’s odd, though, that America is the only person known to have these abilities; even stranger, she stated that she has travelled to over 70 other worlds and has yet to locate a version of herself in any of them. America Chavez appears to be the only one in an infinite multiverse.
The most plausible explanation is that America Chavez is a “nexus entity” in the Marvel Cinematic Universe. The term “nexus” was first introduced to the MCU in WandaVision, but it was never defined; Loki tried to clarify it by discussing the term’s significance in reference to the multiverse’s structure, but that definition didn’t exactly match with the previous context. It’s taken from comic books, where nexi were characterised as “Individuals with the ability to influence probabilities — and consequently the future — are extremely rare. These entities act like rocks and dams, disrupting the passage of time itself… These nexi constitute the multiverse’s core foundations — and are essential to its eventual coherence.” Later comics showed that only one nexus being can exist in a dimension at a time, with Scarlet Witch functioning as the main Marvel timeline’s nexus being. This rule explains why only one America Chavez appears to exist.
It’s reasonable to presume America Chavez is a nexus being in the Marvel Cinematic Universe. While she doesn’t appear to have any probability-altering abilities, Doctor Strange stated that her journey across the multiverse was not as random as it appeared, and that her jumps put her exactly where she needed to be. This was especially clear when she teleported herself and Doctor Strange to Earth-838, a dimension possessing knowledge of the Book of Vishanti and a doorway to assist them in their journey. The chances of this happening are astronomical, implying that America Chavez bends probability in the multiverse. Meanwhile, America Chavez’s presence in a branch of the MCU’s multiverse likely stops it from branching off further; otherwise, every time she made a decision, new varieties of America would be born. Her presence does, in some undetermined way, offer structure to the multiverse.
America Chavez’ abilities meet the description of a “nexus entity” better than any other character in the comics. A nexus is “a means of connection,” a “tie,” or a “link,” according to the Oxford English Dictionary. She has the capacity to build portals between dimensions, allowing her to establish temporary connections between timeframes. If America Chavez was presented as a nexus entity by Doctor Strange in the Multiverse of Madness, then the definition makes a lot of sense.