Captain America woke up from decades of slumber with his body prepared and his mind rested, but his football allegiance was still open for debate. He loved the color brown, because it's a fairly bland early 20th century color, so he chose the Cleveland Browns.
How could he have known any better?
With Cleveland ahead, 30-7, over the Kansas City Chiefs and well on their way to their fifth win in eight games, is there nothing that the Avengers can't do? If the Browns got to .500 this year, that's like defeating Loki times ten.