Avengers: Endgame directors Joe and Anthony Russo have explained Captain America's time travel shenanigans. The final moments of the movie saw Cap head back in time to restore the Infinity Stones to their rightful places – however, his adventures lead to him staying behind with Peggy Carter and reappearing in the present-day considerably older.
There was a bit of confusion about whether Cap had stayed in the main timeline, or ventured into a branch reality – that is, an offshoot of the regular timeline caused by a change made in the past.
"One thing that's clear that [Anthony] and I have discussed… Cap would have had to have travelled back to the main timeline, that's something that, yes he would have been in a branch reality and have to have travelled back to the main timeline to give that shield to Sam Wilson," Joe Russo told the Lights Camera Barstool podcast.
He further explained: "In our internal logic that we defined in the room, that was the choice that we made, was based on everything that happened he would have been in a branch reality and then had to have shifted over to this, so jumped from one to the other, right, and handed the shield off."
This isn't the first time the Russos have clarified Captain America's journey through time. Back in 2019, they explained in a Reddit Q&A that Steve Rogers would've come back to the usual MCU timeline: "He would have had to have worn the quantum suit, using a Pym particle to make the jump [back to the main timeline]. He's not wearing the suit on the bench, because that is not the exact moment to which he returned."
This does clear things up a bit, and potentially leaves the door open for more details on Cap's alternate reality adventures to be explored in some detail later on (though Joe Russo said he has "no idea" what happened in the branch reality). The main point is, Steve made his way back, and handed the shield over to Sam Wilson – though he might not actually end up the new Captain America in the upcoming Disney Plus show The Falcon and the Winter Soldier, which premieres this March 19.
While you wait for more Cap content, Marvel are releasing new episodes of WandaVision every Friday to tide you over.