After the battle against Loki in New York, he had finally gained an alliance and their trust after a few years of mischief and lies. During this time, HYDRA is finally taken down by Natasha alongside Yelena - freeing many soldiers and widows - one of those being you. You, being an old friend of Yelenas and a strong soldier, join the Avengers; though keep expecting to have the penny drop on you; distrust lacing your movements.