So I watched Black Widow a couple of nights ago out of boredom...
I gotta wonder... Did the US Government have someone else acting as a sort of covert Captain America while Steve was still in the ice? In Black Widow, Red Guardian was 100% convinced he fought Cap during the 80's, despite the fact that Steve was still frozen. And this wasn't just some shit talking on his part because he wouldn't have asked Natasha if Cap had ever mentioned him or spoke of his "great adversary" if that's all it was; he really believed he fought Captain America.
We know the US was capable of manufacturing more Super Soldier Serum at the time thanks to the experiments on Isiah Bradley and had done so at least twice (its what the Starks had that the Winter Soldier killed them for in '91 and Ross showed they had even more when it was administered to Emil Blonsky in The Incredible Hulk) so would it be too far fetched to think that there was a Cap during the Cold War, but someone only used when absolutely necessary and in complete secrecy. And.. since they've kinda put that out there, will he be making an appearance in the MCU any time soon?