When Steve Rogers was injected with a Super Soldier Serum, he became the WWII hero and First Avenger, Captain America!
When Captain America was approached by Face Front CEO Joshua Westbrook, he was all too happy to sign up. With several facets of media focused around showcasing different aspects of the Avengers and other heroes, Cap saw it as an opportunity to not to gain the public's trust, but to inspire the next generation of heroes.
Heroes like his friend Sam Wilson, who he made an Avenger on an impromptu phone call during the battle of Sokovia. Sure, he was distracted fighting Sub-Ultron bots, but Captain America wouldn't have made Falcon an Avenger if he didn't mean it from his heart. Unfortunately, he never really had time to follow up on that action, with the city constantly under attack from the likes of Fin Fang Foom.
This came to a head when Cap was called in by Agent Coulson of S.H.I.E.L.D. and interrogated about Wilson. Cap described him as a friend, but was heartbroken to discover that Sam had stolen the Infinity Gauntlet, and intended to use it. Coulson assembled Cap, Iron Man, and Thor to retrieve the Gauntlet, and stop the Falcon, whatever it took.
The three Avengers confronted Falcon, and Cap tried his best to diffuse the situation, telling Sam to put the Gauntlet down, emphasizing that they had no intention of hurting him. However, when Sam escalated, Cap quickly apologized for his negligence, in one last attempt to stop Sam from doing something he would regret. But it was all in vain, and Falcon unleashed the power of the Infinity Gauntlet. (See Infinity Showdown)
After this, Captain America was called by Nick Fury to aid in the Secret War. HYDRA had infiltrated the Triskelion, and taken Maria Hill captive. Cap got in, and began what was supposed to be a quick and quiet mission to retake the Triskelion. He worked his way through waves of HYDRA goons and finally found Hill, only to be attacked by the Winter Soldier. Captain America fought him to a standstill, but soon realized that he had just been pitted against the last friend he had left in the world: Bucky Barnes.