What Happened To Everyone Who Became Captain America?

Recently making a splash courtesy of Wyatt Russell's tremendous performance in The Falcon and the Winter Soldier, John Walker is arguably the most famous of all the Cap replacements to have emerged outside of Steve Rogers' immediate circle. His onscreen depiction isn't quite what is seen in the comics though, where Walker emerges first as someone who believes Rogers is past his prime and needs replacing, as opposed to someone who dutifully assumes the mantle when pressed by the government.

John Walker, like his onscreen depiction, was a combat veteran. However, in the comics, Walker gains his powers from the Power Broker directly and then becomes the privately sponsored hero known as the Super Patriot. After the the Commission on Superhuman Activities steps in to argue that Steve Rogers should answer directly to the government, he abandons the mantle of Captain America and the Commission replaces him with Walker.

Walker quickly proves himself a capable Cap, but he's twice as ruthless as Rogers and is just the right amount of ignorant to be manipulated by the institutions he serves. He eventually realises what's going on though, and assumes the new identity of U.S. Agent thereafter.

As U.S. Agent, Walker would become a member of the West Coast Avengers and slowly but surely turn into a hero in his own right. Not one anywhere near as commendable as Rogers, but you know, it's the thought that counts.